If you have a Mozilla Sync account, you can simply import it. If you don't, the only other way is to get the data from a backup if possible.

To get your data back from a backup, locate this folder in the backup file:

AppData\Roaming\Mozilla

and copy it to

C:\Users\[account username]\AppData\Roaming\Mozilla

If you can't do this, then there's no way to get that data back.

Firefox normally creates backup files for those things. Also, look on your desktop for a folder called; Old Firefox.

Firefox creates that backup folder when you reset firefox to the factory defaults. Resetting the PC does not.