I have the private key. but I don't have the public address or the wallet itself that was saved on an external hard drive that was stolen from me

I lost my bitcoin wallet, I have the key but lost the wallet, it was saved on an external hard drive but was stolen from me,
how I can get my wallet back?

the second question, If someone have bitcoin and have the bitcoin address, but lost the wallet, can the bitcoin be retrieved? and transfer to another wallet?