Modify Prestashop Module of export to Amazon (part_number instead of EAN code)

I have a prestashop store with amazon marketplace module. It is configured with my API data, and works ok with products with ean code. I agreed with Amazon and approved for EAN exemption and i can add products without ean code, but instead of it, i need to send the part_number to Amazon. You have to modify module to permits export part_number instead without EAN code and finally, the products will must be exported to Amazon.