Product ID for a handmade gift set inquiry

Good afternoon all,

I am new to this, I have begun the process of transitioning my store to Amazon but have become stuck adding my first product. The product in question is a gift set which is composed of numerous smoking related accessories all placed on a tray and wrapped. Amazon are requesting a “Product ID” for the products listing but each product has their own barcode including the tray but as a collective do I use the barcode which is visible to the consumer? (The tray) or does a collective code need to be created for the product as a whole?

I appreciate anyones advice! As I said before I have just set up my account so any help would be greatly appreciated.