I would recommend the solution from this question: https://support.mozilla.org/hu/questions/1020790

So, save the pages into bookmarks, then backup your profile before wiping the computer.

Thank you. Could you tell me how to bookmark pages and how to backup my profile?

One way is to copy your Firefox profile As Is to a backup or thumb drive.

Along the lines of FredMcD's last reply, please see:

• Back up and restore information in Firefox profiles
• Recovering important data from an old profile

I also have a converter tool you can use to turn your current session history file into a web page of clickable links. You then can save that in cloud storage (e.g., Microsoft OneDrive, Google Drive, Dropbox) as a further backup.

https://www.jeffersonscher.com/res/scrounger.html