If you want to backup and restore your Firefox Settings, Bookmarks, History, and extensions, you will have to copy the Firefox file from the computer you want to the target computer.

First you will have to make your hidden files viewable.

To backup your Firefox, go to the specified folder, for the Operating system you’re using and copy the entire folder:

Windows XP: C:\Documents and Settings\[user]\Application Data\Mozilla

Windows Vista: C:\Users\[user]\Application Data\Mozilla

Linux: /home/[user]/.mozilla/firefox

Replace [user] with your username.

To restore your backup, go to the same folder and paste the files there.