I have a gift card but there is two numbers mising

Use the zoom feature of the camera of your cell phone. The type may just be too small to read.

Or get a magnifying glass.

If your card has a barcode, bring to someone who has a barcode reader and see if they can read the number off the barcode.

Send it back to the vendor and tell them you can't read the card's serial number, and tell them it faded away if you still can't figure it out.