Hello, I have created a UPC with the GS1 database. However, I want to send 100 units to FBA for fulfillment. How does the warehouse know how many units are in the box that I send? From what I understand I only need a single UPC code for the product that i'm sending.
" How does the warehouse know how many units are in the box that I send?"
Spend the next month studying Seller U since you are NOT ready to sell here at this time.
https://sell.amazon.com/learn
As to packaging for when you are ready --
If you are sending it to FBA think long and hard about the packaging.
It should withstand being dropped off the Empire State Building and being run over by a forklift.
In addition, Amazon has gone 'minimalist' in packaging for shipment. My last several shipments came in plastic bags. One was the package of socks (as sold in stores) with just the shipping label stuck on it.
At least the mail man didn't laugh at my choices. I'm considering buying some thongs just to get a chuckle out of him.
You have to learn how selling on Amazon works. Take 4-5 weeks and learn here:
https://sellercentral.amazon.com/learn
It is difficult and you are at the very beginning. One minor mistake and Amazon will suspend your account forever.