i want to show related post in inside post for example after 3 paragraph, this code is after content is that possible without plugin if yes, so how can do, plz guide with code..

 <ul class="relatedpost">
    <?php
                        $related = get_posts( array( 'category__in' => wp_get_post_categories($post->ID), 'numberposts' => 3, 'post__not_in' => array($post->ID) ) );
                        if( $related ) foreach( $related as $post ) {
                        setup_postdata($post); ?>
                                <li>
                                <a href="<?php the_permalink() ?>" rel="bookmark" title="<?php the_title(); ?>"><?php the_title(); ?></a>
                                </li>
                             <?php }
                wp_reset_postdata(); ?>
        </ul>