Don't close Firefox. If Firefox is closed, do not start it again. Make a backup of your session files. Here's how:

If Firefox is NOT running:

In the Start menu search box, type or paste the following and press Enter:

%APPDATA%\Mozilla\Firefox\Profiles\

Here you should find one or more semi-randomly-named folders. Double-click into the most recently updated one.

If Firefox is running:

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

In the first table on the page, click the "Show Folder" button. This should launch a new window listing your currently active settings files and folders.

Files to copy:

Scroll down and

(1) Double-click into the sessionstore-backups folder. Copy these files to a safe location such as your Documents folder or Desktop.

(2) Back at the main level, scroll down to the sessionstore.js file, if any. If you find one, copy it to a safe location such as your Documents folder or Desktop.

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

• sessionstore.js and/or 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; sessionstore.bak for pre-33 versions of Firefox
• upgrade.js-build_id: the windows and tabs in the Firefox session that was live at the time of your last update; sessionstore.bak-datetime for pre-33 versions of Firefox

If you come up with something promising, you may be able to have Firefox use it for your next session (details if relevant). Does anything look like it's from the right time?

During the update, did Firefox perform a Reset? The usual sign of a reset is that a new Old Firefox Data folder appears on your desktop. Or if you already had that folder, a new profile folder appears inside it.

These files aren't present and the nearest to them are current times. I have closed the laptop after the update although did not shut down Firefox until now to try the other method you posted.

I believe it did a reset as all the pages disappeared and the Firefox homepage opened up. Where can I find the mentioned folder as its not on my desktop