Unfortunately, since unique private keys are associated with individual Bitcoin wallets, if the keys are lost then what I will do?
Maybe you can tell us more about which wallet you use? It becomes easier for people to give you an answer then.
Generally if your private keys are lost your coins are lost. Its as simple as that. There is no way to recover them. If you have a seed phrase which you remember then use that to recover the wallet. Again did you lose the seed phrase?