Sorry tabs cant be re opened if they are closed you can check in history.

When did this occur? Generally speaking, Firefox only saves one session, your immediately previous session, so going back very far in time is difficult.

If Firefox is currently running, please back up your session history files to a safe location for potential recovery/salvage operations.

You can open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter/Return

In the first table on the page, click the "Show in Finder" button.

In the window that launches, scroll down and double-click into the sessionstore-backups folder. Save all files here to a safe location, such as your Documents folder. Although some of these files are too recent to be of use, perhaps an older one will be helpful.

The kinds of files you may find among your sessionstore files are:

• recovery.js: the windows and tabs in your currently live Firefox session (or, if Firefox is closed, your last session)
• recovery.bak: a backup copy of recovery.js
• previous.js: the windows and tabs in your last Firefox session
• upgrade.js-build_id: the windows and tabs in the Firefox session that was live at the time of your last update

If you consider the date/time of the various files, do any seem likely to have the missing tabs? If so, we could discuss options for loading the old session or extracting out the list of tabs from it.

Also, could you check your desktop for an "Old Firefox Data" folder? If the Firefox Refresh feature ran, your old settings folder would be inside there and depending on when that happened, it might contain a relevant session history file.