Cubase 5 license key is registered on an old account

Hello everyone. i have a problem.
i have Cubase 5 with a usb license, now i had an account with the product registered on it but i cant remember and i dont have any mail that i can find it on. i want to upgrade to cubase 8.5 but i have to transfer the license key the my new account is there anyway to do it? please help me i tried some things in MyProducts and it didnt work! :cry:

please can anyone help me with that?

can i download the 8.5 upgrade to my soft elicenser and move it to my usb and upgrade my cubase 5 license that is in there?