What do you mean repair Windows 10? If this means restore to last working image then anything after that restore means all data is gone and if Firefox folder is wiped clean or removed then all data is gone as well and there's nothing to recover or restore at this point. So unless there was devices sync prior to this happening then then following Firefox sync help would try but if there is no Sync then nothing can be done as there is nothing to restore or recover anymore.

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

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
• https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update