Get wordpress image sizes

How can I get the WordPress images based on size.

By default, wp makes a thumb which is 150×150, makes a medium pic which is 640×640 and makes a large image which is 1024×1024.

Right now from my template I am doing this:

if ( class_exists('Dynamic_Featured_Image') ) {
    global $dynamic_featured_image;
    $post_more_image = $dynamic_featured_image->get_featured_images( get_the_ID() );
}

if (!$post_more_image == ''){
                    foreach($post_more_image as $post_more_img) {

                        $full_image = wp_get_attachment_image_src( $post_more_img['attachment_id'], 'full' );
                        $full_width = $full_image[1];
                        $full_height = $full_image[2];

                ?>
                <div class='col-xs-6 col-sm-4 col-md-3 col-lg-2'><a href='<?php echo $post_more_img['full']; ?>' data-size='<?php echo $full_width; ?>x<?php echo $full_height; ?>' data-med='<?php echo $post_more_img['full']; ?>' data-med-size='<?php echo $full_width; ?>x<?php echo $full_height; ?>' data-author='<?php the_author_meta('display_name'); ?>' class='demo-gallery__img--main'><img class='lazy' data-original='<?php echo $post_more_img['thumb']; ?>' /><figure><?php the_title(); ?></figure></a></div>
                <?php
                    }

This gets the full size image fine
wp_get_attachment_image_src( $post_more_img[‘attachment_id’], ‘full’ );

But then I try instead of the word full, I tried thumb, medium, large and medium, large are not working. Any suggestions? I logged in and looked at my upload and see 4 images for each picture uploaded. The full size image, the large which is 1024, and the medium which is 640 and the thumbnail which is 150

https://wordpress.org/plugins/dynamic-featured-image/