there is an explanation here
https://en.bitcoin.it/wiki/Wallet_import_format

and some online thing here
https://gobittest.appspot.com/PrivateKey
but you don't paste real keys into online things.  maybe run javascript offline.

or find some python that does it.  here is something:
https://bitcoin.stackexchange.com/questions/58114/convert-wif-to-private-key