You need to send the suppliers below-mentioned things:
Please ask the supplier to paste the UPC and Product set/unit packaging labels on each unit along with your brand name (if any). They will paste the cartoon labels on each cartoon along with Made in China if the target market is USA. In some cases (depending on the categories), you need to put other things as well, like suffocation warning labels, etc.
UPC are the barcodes which you will need to list the item in amazon seller central. However FNSKU are the labels which you will send to your manufacturer and they will print on the box labels. Ask your supplier for DDP shipment do everything will be on supplier headache you don’t need to worry about it.