The crypto code that you attached looks like a Wallet Import Format (WIF), which is a way of encoding a private key in base. A WIF can be used to import a private key into a wallet program.
However, just because it looks like a WIF, it doesn’t mean that it is a valid one. There are some checks that you can do to verify if it is a genuine private key that corresponds to a bitcoin address.
One way is to use a tool like bitaddress.org or cryptex to decode the WIF and see the public key and the bitcoin address that are derived from it. Then you can compare the bitcoin address with the one that you used to receive the bitcoin in 2015. If they match, then you have found your private key.
Another way is to use a programming language or a command line tool to perform the same steps as above, but with more control and security. You can find some examples of how to do this in Python or grep.
I hope this helps you to recover your bitcoin. Please be careful when handling your private key, as anyone who has access to it can spend your bitcoin. It is recommended to move your bitcoin to a new address that is generated by a secure and reputable wallet program.
Good luck!
