Gamestop voucher for money?

Hi

I recently received a 30 euro voucher for the gamestop and would like to get Formula 1 2020, which I found on the Internet much cheaper than at the gamestop

Now my question: How do I get my money from the voucher? There are no Pay Safe cards at Gamestop but only PlayStation credit

Not at all. That is not possible. It actually says on it