Hello,
This demo is using Custom WooCommerce Builder layouts, which are part of WooCommerce Builder from WoodMart.
Navigate to Layouts > Edit Product Archive layout > Edit Product Archive widget and change the product columns.
Further, you can read more about the Layout Builder here:
https://xtemos.com/docs-topic/woodmart-woocommerce-layout-builder/
If you have any questions, feel free to contact us.
Best Regards,