Old wallet

Have found an old wallet address and what I think is a 54 character private key from an old HDD. This is from 2011 when I mined bitcoin for a short while. Because it was so long ago, I can't remember where I created the wallet or what type it is.

Is it possible at all to retrieve the bitcoin?

I've tried mycelium and the wallet address shows my wallet, but when I try adding what I think is the private key it says "Unrecognized format".

My knowledge of using bitcoin is practically non existent so any help would be appreciated.

Thank you