If you have your private key in the format you say, in order to import your key into bitcoin core, you need to convert your key into "WIF" format first.

I guess if you exclude the question marks, you should have 66 characters. However a private key has 64 characters.

One question: What are the first 2 digits of your key? (Do not tell me of course) If the first 2 digits are "80" (eighty) there might be a chance your key is a private key that you prepended 2 digits (80) to it.

For the process of converting to WIF, the first step is adding that number at the beggining.

These are the links I found:

Convert private key to WIF: https://en.bitcoin.it/wiki/Wallet_import_format

Encoding to base58: https://en.bitcoin.it/wiki/Base58Check_encoding

Finally, importing WIF to bitcoin core: https://en.bitcoin.it/wiki/Help:How_to_import_private_keys_in_Bitcoin_Core_0.7%2B#Run_Import_Command_in_Debug_Window