Hi Vincent, if you want to rely on Sync, the key thing is NOT to reset your Mozilla Account password. Resetting your password without using a recovery code flushes your data from the Mozilla Cloud.

Quick initial question, though: did you use an internal Windows feature to reset Windows, the one where it asks whether you want Windows to save your data? In that case, you might have your previous data files on disk and we can suggest where to find them. If not, if you used a recovery disk/recovering partition or formatted the disk, then you might not have any local files to recover from.

Do you know for sure that you used your Google email address as your Mozilla Account username? Perhaps you can tell from an old email sent to your account from "accounts@firefox.com" when you set up the account or when you last signed into it.

If that is the correct email, then it's a matter of remembering what password you used. Easier said than done, I know.

Hi jscher2000, I did not use internal feature to reset Window 7 but instead reformat and reinstalled using "Firefox Setup 115.4.0esr". Unfortunately I did not save any data at all and this was my oversight. I managed to view my Mozilla account under "accounts@firefox.com" (Thank You !) and under Security saw my password in dotted form created in 2017. Unfortunately again I forgotten the actual password (sign!) created. However I copy/paste this dotted form password to Firefox "Sign In" to synchronise and EUREKA !. All my past history and bookmarks are restored  ! Now I better start updating those recovery options.

Thank you again for your insights Vincent Ang

Good solution! Thank you for reporting back.

And you may want to make a backup of your profile folder for any future just-in-case scenarios: Back up and restore information in Firefox profiles.