But that's if you can get something like that from your backup, only if it starts exactly with "0x", otherwise it's a 66character hex or not.
64 characters is exactly the length of a Bitcoin Private key in hex. (excluding 0x)

To use it: You just have to encode it into WIF private key to be compatible with almost all wallets.
There are a couple of tools that can do that, the working fork of brainwallet tool has one but do not attempt it using the web version or on an online machine.
If you wan't to use the tool, get its source code (GitHub link), audit it if possible, extract and launch its index.html file using your offline machine's browser.
Go to 'Convert' tab, toggle "HEX" as 'Source Encoding' and 'Convert to' "B58Check"; type/paste to convert it into WIF.