On Walmart, product data is associated with identification codes such as UPC, EAN, GTIN etc. If the ID code is for a single unit of product you will not be able to list it as a multipack. You will need a separate code for a multipack listing.
Each of the below products have unique UPC, EAN or GTIN code assigned on Walmart:
You can search for the ID code information on websites like BarcodeData.org. To buy new UPC codes for your products you need to reach out to GS1.