itemprop="ratingValue"

I want to add the schema (microdata) by myself and not by using a plugin.
I want to add the following property but I can’t find where to add it in the code:
itemprop=”ratingValue”

The code I use to get the ranking is:
<?php if(function_exists(‘the_ratings’)) { the_ratings(); } ?>

https://ww.wp.xz.cn/plugins/wp-postratings/