hii

please try it to restore this data:

On the desktop you should see a folder called 'Old Firefox Data' open it and copy all the data by highlighting and selecting everything in that folder, then right click and select copy. Now open FIrefox. Head on over to about:profiles by typing it in your URL bar. Click on the Open Folder button under the Local Directory, not root. Then right click when inside the new profile folder and select paste. Then restart Firefox. You should now have all your previous bookmarks, and data back.

after try this if you haven't recovered bookmarks these steps to recover bookmarks

   Use one of these methods to open the Bookmarks Library window: ...
   At the top of the Library window, click on Import and Backup and select Restore.
   Click the date of the bookmark backup you want to recover.
   In the new window that appears, click OK.

Hello,

Sorry to hear about that. First, Firefox automatically creates backups of your bookmarks, which can be helpful if your bookmarks are lost or missing.

   Click the Bookmarks button  and select Show All Bookmarks.
   At the top of the Library window, click on Import and Backup and select Restore.
   Click the date of the bookmark backup you want to recover.
   In the new window that appears, click OK.
   Your bookmarks from the selected date should now be restored. 

Hope it will fix your problem

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Type about:profiles<enter> in the address bar. How many profiles are listed? How many should be there? Also, open the profile folder in your file explorer.