How to display taxonomy terms in a dropdown on a user edit pag

Hello, team. I used a snippet from online to create a user taxonomy which displays the list of the taxonomy terms as a checkbox format. However, I want to display the terms in a dropdown style and must be required to add any user or update the user profile from WordPress. When I use the code below it displays blank where it would display the dropdown.

<?php
// Register Custom Taxonomy
function custom_taxonomy() {

  $labels = array(
    'name'                       => _x( 'Departments', 'Departments Name', 'text_domain' ),
    'singular_name'              => _x( 'Department', 'Department Name', 'text_domain' ),
    'menu_name'                  => __( 'Departments', 'text_domain' ),
    'all_items'                  => __( 'All Departments', 'text_domain' ),
    'parent_item'                => __( 'Parent Department', 'text_domain' ),
    'parent_item_colon'          => __( 'Parent Department:', 'text_domain' ),
    'new_item_name'              => __( 'New Department Name', 'text_domain' ),
    'add_new_item'               => __( 'Add Department', 'text_domain' ),
    'edit_item'                  => __( 'Edit Department', 'text_domain' ),
    'update_item'                => __( 'Update Department', 'text_domain' ),
    'view_item'                  => __( 'View Department', 'text_domain' ),
    'separate_items_with_commas' => __( 'Separate department with commas', 'text_domain' ),
    'add_or_remove_items'        => __( 'Add or remove departments', 'text_domain' ),
    'choose_from_most_used'      => __( 'Choose from the most used', 'text_domain' ),
    'popular_items'              => __( 'Popular Departments', 'text_domain' ),
    'search_items'               => __( 'Search Departments', 'text_domain' ),
    'not_found'                  => __( 'Not Found', 'text_domain' ),
    'no_terms'                   => __( 'No departments', 'text_domain' ),
    'items_list'                 => __( 'Departments list', 'text_domain' ),
    'items_list_navigation'      => __( 'Departments list navigation', 'text_domain' ),
  );
  $args = array(
    'labels'                     => $labels,
    'hierarchical'               => true,
    'public'                     => true,
    'show_ui'                    => true,
    'show_admin_column'          => true,
    'show_in_nav_menus'          => true,
    'show_tagcloud'              => true,
  );
  register_taxonomy( 'departments', 'user', $args );

}
add_action( 'init', 'custom_taxonomy', 0 );

  /**
 * Admin page for the 'departments' taxonomy
 */
function cb_add_departments_taxonomy_admin_page() {

  $tax = get_taxonomy( 'departments' );

  add_users_page(
    esc_attr( $tax->labels->menu_name ),
    esc_attr( $tax->labels->menu_name ),
    $tax->cap->manage_terms,
    'edit-tags.php?taxonomy=' . $tax->name
  );

}
add_action( 'admin_menu', 'cb_add_departments_taxonomy_admin_page' );

/**
 * Unsets the 'posts' column and adds a 'users' column on the manage departments admin page.
 */
function cb_manage_departments_user_column( $columns ) {

  unset( $columns['posts'] );

  $columns['users'] = __( 'Users' );

  return $columns;
}
add_filter( 'manage_edit-departments_columns', 'cb_manage_departments_user_column' );

/**
 * @param string $display WP just passes an empty string here.
 * @param string $column The name of the custom column.
 * @param int $term_id The ID of the term being displayed in the table.
 */
function cb_manage_departments_column( $display, $column, $term_id ) {

  if ( 'users' === $column ) {
    $term = get_term( $term_id, 'departments' );
    echo $term->count;
  }
}
add_filter( 'manage_departments_custom_column', 'cb_manage_departments_column', 10, 3 );

/**
 * @param object $user The user object currently being edited.
 */
function cb_edit_user_department_section( $user ) {
  global $pagenow;

  $tax = get_taxonomy( 'departments' );

  /* Make sure the user can assign terms of the departments taxonomy before proceeding. */
  if ( !current_user_can( $tax->cap->assign_terms ) )
    return;

  /* Get the terms of the 'departments' taxonomy. */
  $terms = get_terms( 'departments', array( 'hide_empty' => false ) ); ?>

  <h3><?php _e( 'Departments' ); ?></h3>

 <?php }

/*fucntion to display taxonomy terms in a dropdown*/
function cb_taxonomy_select_meta_box($user, $box) 
{

  $defaults = array('departments' => 'departments');
  
  if (!isset($box['args']) || !is_array($box['args']))
      $args = array();
  else
      $args = $box['args'];
  
  extract(wp_parse_args($args, $defaults), EXTR_SKIP);
  
  $tax = get_taxonomy($departments);
  $selected = wp_get_object_terms($user->ID, $departments, array('fields' => 'ids'));
  $hierarchical = $tax->hierarchical;
  ?>
  <div id="departments-<?php echo $departments; ?>" class="selectdiv">
    <?php 
      if (current_user_can($tax->cap->edit_terms)): 
        if ($hierarchical) {
          wp_dropdown_categories(array(
             'departments' => $departments,
             'class' => 'widefat',
           'hide_empty' => 0, 
             'name' => "tax_input[$departments][]",
             'selected' => count($selected) >= 1 ? $selected[0] : '',
             'orderby' => 'name', 
             'hierarchical' => 1, 
             'show_option_all' => " "
          ));
        } else {?>
          <select name="<?php echo "tax_input[$departments][]"; ?>" class="widefat">
            <option value="0"></option>
            <?php foreach (get_terms($departments, array('hide_empty' => false)) as $term): ?>
              <option value="<?php echo esc_attr($term->slug); ?>" <?php echo selected($term->term_id, count($selected) >= 1 ? $selected[0] : ''); ?>><?php echo esc_html($term->name); ?></option>
            <?php endforeach; ?>
          </select>
        <?php 
        }
      endif; 
    ?>
  </div>
  <?php } /*end of code which displays terms in a dropdown on a user edit page*/

add_action( 'show_user_profile', 'cb_edit_user_department_section' );
add_action( 'edit_user_profile', 'cb_edit_user_department_section' );
add_action( 'user_new_form', 'cb_edit_user_department_section' );

/**
 * @param int $user_id The ID of the user to save the terms for.
 */
function cb_save_user_department_terms( $user_id ) {

  $tax = get_taxonomy( 'departments' );

  /* Make sure the current user can edit the user and assign terms before proceeding. */
  if ( !current_user_can( 'edit_user', $user_id ) && current_user_can( $tax->cap->assign_terms ) )
    return false;

  $term = $_POST['departments'];

  /* Sets the terms (we're just using a single term) for the user. */
  wp_set_object_terms( $user_id, $term, 'departments', false);

  clean_object_term_cache( $user_id, 'departments' );
}

add_action( 'personal_options_update', 'cb_save_user_department_terms' );
add_action( 'edit_user_profile_update', 'cb_save_user_department_terms' );
add_action( 'user_register', 'cb_save_user_department_terms' );

/**
 * @param string $username The username of the user before registration is complete.
 */
function cb_disable_departments_username( $username ) {

  if ( 'departments' === $username )
    $username = '';

  return $username;
}
add_filter( 'sanitize_user', 'cb_disable_departments_username' );

/**
 * Update parent file name to fix the selected menu issue
 */
function cb_change_parent_file($parent_file)
{
    global $submenu_file;

    if (
      isset($_GET['taxonomy']) && 
      $_GET['taxonomy'] == 'departments' &&
      $submenu_file == 'edit-tags.php?taxonomy=departments'
    ) 
    $parent_file = 'users.php';

    return $parent_file;
}
add_filter('parent_file', 'cb_change_parent_file');

?>