Assuming that you are using WooCommerce, I would be looking for an alternate method of adding custom fields to the WC checkout process other than using ACF. I would guess that there is some type of plugin that will let you add fields for collecting information like this, but I am not familiar enough with it to know for sure.
A quick search turned up the following
https://woocommerce.com/products/product-add-ons/
https://www.modernmarketingpartners.com/2014/11/25/add-sizes-woocommerce/
