The UPC (Universal Product Code) is a barcode (which has numbers beneath it) which identifies the product and the manufacturer. I think you may be thinking of the PLU (Price Look Up) code which is the 4 or 5 digit number on produce used to link a price with an item. The PLU code is a voluntary program that assigns numbers to produce items, this helps cashiers identify the correct price for a produce item.
Growers/Packers can use the number "9" prefix to this 4-digit numeric code to identify fruit and vegetable items that are USDA organic. Initially it was proposed that the "8" prefix would be used for "genetically engineered" aka "GMO' however it is not used for this purpose.