- Head to
C:\Users\%USERNAME%\AppData\Roaming\Mozilla\Firefox\Profiles\
- Copy/Backup the directory in some place safe
Do you have multiple directories? that means you have multiple Firefox's profiles, in most cases xxxxxxxx..default is the main one (if you have multiple Firefox's profiles, you are pro user, what the hell you doing here?!)
- Head to
C:\Users\%USERNAME%\AppData\Roaming\Mozilla\Firefox\Profiles\
- Open up
xxxxxxxx.deafult
directory - Copy entire content of backup directory to opened directory
- Turn off your PC, just kidding, your are done, start Firefox