?php echo get_the_post_thumbnail_url(get_the_ID(), 'full'); code example
Example 1: get featured image url
echo get_the_post_thumbnail_url();
Example 2: wordpress get post thumbnail url
<?php
// ALL parameters are optional. Not needed if you are on WP LOOP
echo get_the_post_thumbnail_url( $the_query->ID, array( 500, 400) ); ?>