Reinstalling Firefox shouldn't affect your configuration.

But it wouldn't hurt to back up your Profile folder, just in case. https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Thank you but i wish to reinstall windows as well do i just save the backup on a removable disk

Or a USB Flash stick.

If you are talking about a CDR disk, you may have a problem after restoring your Profile with having a "lock" on the individual files due to using a CDR and Firefox not working properly or an "alert" popping up. Easily solved by being observant after restoring your Profile and unlocking those files.