Show Related posts loop based on tags

Question

I want to show tag based post in related post. Here is the complete template code for my related post loop (loop.related.post. php ) What changes do I need to make in this loop? My theme is custom. I want to show 6 posts in related posts.

<?php
global $wpdb, $post, $wp_query;
$URLs_Link_MP3 = get_post_meta( $post->ID, 'URLs_Link_MP3', true );
$durations_MP3 = get_post_meta( $post->ID, 'durations_MP3', true );
if(!$durations_MP3) $durations_MP3 = '0';
global $wpdb, $post, $wp_query;
$durations_MP3 = get_post_meta( $post->ID, 'durations_MP3', true ); if(!$durations_MP3) $durations_MP3 = '0';?>
<div class="col-sm-6 item" data-id="<?php the_ID(); ?>" data-value="<?php echo $URLs_Link_MP3 ; ?>" >
    <div class="row">
        <div class="button dark player loader" duration="<?php echo $durations_MP3 ; ?>">
            <svg class="icon icon-play">
                <use xlink:href="#icon-play"/>
            </svg>
        </div>
        <a class="details" href="<?php the_permalink() ?>" title="<?php the_title(); ?> PDF Download">
            <h2 class="title"><?php the_title(); ?></h2>
            <p><?php echo $durations_MP3 ; ?> <?php global $opt_themes; if($opt_themes['rtones_Sec']) { ?><?php echo $opt_themes['rtones_Sec']; ?><?php } ?> - <?= ex_themes_get_post_view_(); ?> <?php global $opt_themes; if($opt_themes['rtones_Author_Download']) { ?><?php echo $opt_themes['rtones_Author_Download']; ?><?php } ?></p>
        </a>
    </div>
    <?php global $opt_themes; if($opt_themes['ex_themes_tags_all_active_']) { ?>
        <div class="row">
            <?php
            $post_tags = get_the_tags();
            if ( ! empty( $post_tags ) ) {
                echo '<ul class="tags">';
                foreach( $post_tags as $post_tag ) {
                    echo '<li><a href="' . get_tag_link( $post_tag ) . '">' . str_replace('ringtones', ' ', $post_tag->name) . '</a></li>';
                }
                echo '</ul>';
            }   else {
                echo '<ul class="tags">';
                echo '<li><a>no tags</a></li>';
                echo '</ul>';
            }
            ?>
        </div>
    <?php } ?>
    <div class="row">
        <div class="actions">
            <div class="button light fav">
                <?php if ( shortcode_exists( 'favorite_button' ) ): ?><?php echo do_shortcode( '[favorite_button]' ); ?><?php else: ?><?php endif;?>
            </div>
            <div class="button light share">
                <svg class="icon">
                    <use xlink:href="#icon-share"/>
                </svg>
            </div>
            <a href="<?php the_permalink() ?>" title="<?php the_title(); ?>">
                <div class="button dark download">
                    <svg class="icon">
                        <use xlink:href="#icon-download2"/>
                    </svg>
                </div>
            </a>
        </div>
    </div>
</div>