On your hard drive, look for a folder called Windows.old
Is it there?

I found it.

Everything from the original should be in that folder.

You can copy files like these with Firefox closed to the current profile folder to recover specific data.

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

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (passwords) and key4.db (58+) or key3.db (57 and older) (decryption key) for Passwords saved in the Password Manager
  if you only have key3.db then make sure to remove an existing key4.db
• cert9.db (58+) or cert8.db (57 and older) for (intermediate) certificates stored in the Certificate Manager
  if you only have cert8.db then make sure to remove an existing cert9.db
• persdict.dat for words you added to the spelling checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

I found it.

Set Windows to show hidden files and folders in order to explore it:

https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

Then, your previous Firefox data is along the following path.

C:\Windows.old\Users\username\AppData\Roaming\Mozilla\Firefox\Profiles

Somewhere in there? Now see the above comments about the key files to recover.

Since C:\Windows.old is a temporary folder, move anything important to a real folder so Windows doesn't flush it before you have a chance to restore.