It sounds like that drive was plugged into your PC or laptop when you got hit by the virus.
Ransomware viruses will encrypt
ALL connected storage drives physically connected to your PC or laptop, and ask you for money in order to unlock the files on those drives as well as the main drive.
Do you recall seeing a pop-up box with a phone number or any kind of message asking you to pay to get access to your files again?
The Windows backup system is not reliable in my opinion, and several of us professionals here do not trust nor use it.
I would suggest that you remove that external drive (USB?) from your computer and set it aside for professional data recovery. You will then need to pay attention to the computer itself. Can you access files on the internal hard drive in your computer using File Explorer in windows?
(you mention accessing your files via Control Panel, and that program will not let you do that; so I think you were talking about the W10 File Explorer file management program).
If you cannot access files on your internal hard drive, then most likely you didn't remove the virus properly, or the removal process permanently damaged your windows.
Once you post back the answer to this question, we can give you suggestions to repair it. Certainly, you'd want to pay a visit to our Windows Security forum and get more help on disinfecting your computer.
If you can access files on your internal hard drive ok, then you may have simply experience a coincidental hard drive failure on that external drive. You can attempt DIY data recovery on your own, but if you've never done it before or at not experienced at doing so, you should seek the help of a professional computer Tech at your local repair shop and pay him to get whatever you can off of that drive. The Tech will usually provide you your files on backup DVD discs, a flash drive, or another new replacement hard drive. You can then re-attach your backup media to your disinfected computer and access your files or copy them back over to your computer.
**CAUTION**: If you make attempts to run data recovery on a ransomware encrypted drive, you can scramble your data beyond any kind of local recovery Tech's ability to fix and it will have to be sent out to very very expensive professional data recovery. FYI.
Let us know some answers and we'll advise you further.
<<<BIGBEARJEDI>>>