I finally found the backup I wrote down after using Gavin Andresen's Bitcoin faucet. I don't remember if I was using only Bitcoin Core, Armory, or something like Multi-bit. Those sound familiar.

There are 5 bitcoins in the first address and I never moved or used them. The characters I found on my handwritten paper backup are 80 characters, between (0-9) and (A-F). I wrote these in blocks of four characters. Within these 80 characters, I have 14 question marks. So a total of 66 known characters. I'm not sure if I only need 64, 66, or 80 characters total.

I have Bitcoin Core and Electrs downloaded on my Umbrel to start trying the recovery process. I also have Electrum and Armory downloaded.

I'm not sure the best course to go from here to find out what the key may be and how long it should be. I'm not in a hurry and have time to try to figure this out, hopefully with your help.

Offering a full Bitcoin to the best helper.