1
Try to work out any missing characters in the product key, these are the characters that cannot appear in a Windows product key.
Letters: A, E, I, L, N, O, S, U, Z
Numbers: 0, 1, 5
2
If you are still unable to work out the product key, this forum is just a user to user forum, you will need to contact Microsoft Support directly, provide them with proof of purchase and the other details on the product key card, they may be able to provide you with the associated product key.