Also create (export) an HTML formatted backup file that can be viewed and/or imported on any browser.
Ctrl+Shift+B to bring up the Library List
"Import and Backup" menu
choose "Export HTML..."
prefix suggested name with drive letter for thumb drive, i.e. f:\bookmarks.html
This file you can view anywhere as an HTML file if your computer breaks before you have a replacement.
You really want to backup your entire Firefox profile(s), in addition, you would be able to replace the content of the Firefox profile on your new system with this if you can't or don't restore your entire users application profile on your system. This should also fit on most thumb drives and will contain all of your settings, extensions, bookmarks, bookmarkbackups, etc. as seen in
Steps to backup entire Firefox profile on a Windows machine to a thumb drive
Find where you current profile is by typing in about:support into the Location Bar, or through Help > Troubleshooting information...
Press the "Open Containing Folder"
You are now in your current folder, but lets go up three directories to the "Mozilla" directory
Bring Firefox completely down, through File > Exit, wait for Firefox to close and verify in the "Processes" tab of the Windows Task Manager that firefox.exe is not running.
Select "Firefox" directory, right click, and choose "Copy"
Select your thumb drive i.e. F:/ and Paste (Ctrl+V) into the thumb drive, that should copy all of your Firefox folder, and all subfolders. Hopefully being a windows user you don't have read-only, or hidden files in there.
When it comes to restoring on a new system or a new hard drive you would restore the profiles.ini and the Profiles folder into replacing what was generated for you when you install Firefox on new system or new hard drive.
If you still have a running system, you probably want to purchase an external HD, preferable USB-3 thinking for the future, and backup all of your application files to it. See http://dmcritchie.mvps.org/windows-7/win7.htm for what you would be doing when populating a new system.
A lot of your application data will be in your application folder type the following into Windows Explorer (My Computer) or into the Run box -- %APPDATA% and back that up to your hard drive it may take 6-12 hours or longer. But you probably have data document files of your own also, back them up first. This backup would include your Firefox profile but you probably want to use the one for Firefox created on your thumb drive and selective restore portions of this file when the time comes to restore, since your new system would probably be Windows 7 (unless you just replaced the HD).
I think you have everything here, but you might also want to check out a similar question in