I have not tried upgrading from 3.5 to 10 or 13, but see no reason why the cookies should be lost.

Are you using multiple versions of Firefox, if so to prevent problems you should use a separate profile for each version. To try to prevent loss of cookies back up your Firefox profile and keep it somewhere safe outside of any firefox program or profile path.

I am not sure what you are now trying to do. If your cookies are already deleted then you now have no cookies to loose on updating. Or is it some other setting or data you are concerned about.

See also

• http://kb.mozillazine.org/Cookies#Where_are_cookies_stored
• http://kb.mozillazine.org/Multiple_cookies_files_created
• Back up and restore information in Firefox profiles
• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

Firefox should import and convert the cookies from a cookies.sqlite file used in Firefox 3.5.

Be aware that websites may invalidate cookies if they detect a browser change via the user agent.

Also Firefox will upgrade SQLite database files if you access such files with newer Firefox versions, making them incompatible with Firefox 3.5.

• SQLite Manager: https://addons.mozilla.org/firefox/addon/sqlite-manager/