finding serial number from box

The barcode will not provide a serial number.  The serial number would not be visible in any way on the external portions of the packaging.  Serial numbers contain 24 numbers, usually as 6 groups of 4 numbers.

"Depending on the product, your code may be on the disc sleeve (serial number), on an insert card (redemption code), or on the product box."

(Find your serial number quickly)

It might be the 18 number code you've found.