To add onto the comment below: Do you have your public/private keys? Can you see your account on https://stellar.expert ?

Because you may have the legacy login info and recovery code, there might be a chance that an SDF member can help you. I am not 100% sure though since you said you already upgraded.

Did you use any specific Wallet UI's when you upgraded? Or were you only given a public/private key-pair that you used in the Stellar account viewer?

If you do not have your private key backed up anywhere, technically you won't be able to retrieve them since Stellar accounts only work off public/private key pairs. Other wallets which may be custodial allow access to the wallet by having you put in a username/password/2FA etc. That way if your computer dies or your long-term memory fades, you can still try to access the wallet using other methods. Custodial wallets, like exchanges, control the secret key however so you're not 100% in control at all times.