You can use wpto_thumbs_size
filter to resize thumbnail. Read this article to learn about how to use filter and action hook.
Here I have added a snippet. Add this snippet to end of the child theme's functions.php
file.
if( !function_exists( 'wpt1234_resize_the_thumb_size' ) ) { function wpt1234_resize_the_thumb_size () { return 'woocommerce_thumbnail'; } } add_filter( 'wpto_thumbs_size', 'wpt1234_resize_the_thumb_size' );