SHA256, mate, is actually a hashing algorithm used in the Bitcoin network. It's not a format for private keys.

A Bitcoin private key is simply a random number between 1 and about 10^77. This number is often represented in Wallet Import Format (WIF) which looks like a string of letters and numbers starting with "5" or "K".

But remember, whatever format your private key is in - keep it safe! It's your ticket to your bitcoins.