¿How to list a Multi-pack product?

Im trying to list a new product on Seller Central, its a beauty product Multi-pack (same product, but 3 units) btw im doing wholesale. The issue I have is this 3 units Multi pack doesnt exist on Amazon, so I have to create a new Amazon Listing. Do I need to file for a GTIN exception? Which UPC do I use? Or how do I get to use this brand? Thanks