I’m using Woocommerce for products. All products are imported automatically by a plugin.
now i input product url for affilliate shop and change in the source product link

affilliate link format is:

product url= affilliate user code + website address + metadata

affilliate user code: affuser/kjhygdfdh  
website address: https://www.affsite.com      
metadata: get_post_meta($post->ID, 'affmeta',true)  
product url woocommerce meta data: _product_url

i need in function get meta key and add to affilliate user code + website address then input in product url in woocommerce

Note: I have all of the above and it is a fixed link

A friend said I should use the following functions (save_post,get_post_meta,update_post_meta)
But I don’t know where and how to do it