Someone have idea? about category

<?php
$posts = get_posts('numberposts=3&category=4');
global $post;
?>
<?php if($posts): foreach($posts as $post): setup_postdata($post); ?>

<div class="">
<?php get_template_part( 'content', get_post_format() ); ?>

<a href="<?php the_permalink() ?>" >
<?php the_post_thumbnail( 'sydney-medium-thumb' ); ?>
</a>
</div>

<?php endforeach; endif;?>

I want to display posts of any category on some posts.
Any one have some idea about display posts of category.
or must make category.php ?

Plugin “List category posts” can work.
Plugin “Content Views” cannot work.
Plugin “Post Category” can work.