hello, you might want to inspect your harddrive for traces of your old profile folder: Profiles - Where Firefox stores your bookmarks, passwords and other user data

i don't know how and from which OS you have upgraded but that may have involved a reformat of your harddrive. in this case you cannot restore your prior bookmarks without an available backup...

Did Windows create a C:\Windows.old folder?

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

These can't get your data back, but will help in the future.

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences