This author asked if they have to provide the barcode and ISBN on the backcover when they upload their paperback book to Amazon KDP or IngramSpark.

The simple answer is: NO
If you have not purchased or created a free barcode then you do not have to provide on. Amazon KDP and IngramSpark can generate a no price barcode that will show up on your paperback or hardcover book. They will pull in the ISBN you provided so that it appears.

If you want the price on your barcode and have a barcode with the price, then yes, include that on the cover file when you upload. For Amazon KDP you will need to select the box that says you already have the barcode.