I'm going offline now but get_the_post_thumbnail_url and the_post_thumbnail_url are functions so you call them like this
Code:
<?php get_the_post_thumbnail_url(); ?>
<?php the_post_thumbnail_url(); ?>
Check the WP reference for usage (image size etc):
https://developer.wordpress.org/refe...thumbnail_url/
https://developer.wordpress.org/refe...thumbnail_url/