If you redeemed it for the wrong region you will have to contact support and ask them to help you if they can. They might be able to help but there is no means to do it otherwise. Good luck!
Also for future reference you can post questions like these in the Oasis forum:
Unfortunately, the Prime Gaming codes (or at least the currently-active promotion) are only available for Black Desert Online NA/EU/SA servers and Black Desert Console (Xbox/PlayStation).
SEA is not included. so you can't get the content of the code to your SEA account.