Do you still have any profile data like a backup assuming that you had to reinstall Firefox and all other applications ?

You can check if you have a C:\Windows.old folder with your Firefox profile data.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

Just to clarify, which is the most like what happened:

• power outage crash -- everything is where it was, but not working correctly
• used the Windows Reset/Refresh feature and told Windows to save your data
• used a recovery disk/partition to rebuild the system from scratch, nothing survived

You mentioned an Old Firefox Data folder. Do you have an Old Firefox Data folder on your Windows desktop? If so, double-click into that folder and any sub folders and check the files in the "bookmarkbackups" subfolder. These have their creation dates coded into the file names, so you can get an idea of how old they are.