For example Oreos…. Put it in a box? Do you use bubble wrap?
Order from amazon, Oreos in the same package as you are selling and use the same level of packaging that amazon uses.
Its called leader ship by example, if it is cheap and flimsy do the exact same thing as amazon. You are in this to make money, some day you might have a yacht.
You can place FBA barcodes on the outer side of each pack of Oreos, so that you cover the original manufacturer barcode with your FNSKU.
As others said or you can let Amazon prep them for you if you want.
Cookies would probably arrived crushed by the time they get to the customer. Oreos packaging isn’t great. I’d bubble wrap if I was sending in cookies.