Updates are a choice or lack of, you make, they are not forced on you, you may have opted/selected to have it automated. Check that so it will not happen again.

So is this a RaspberryPi (aarch64) I am using such now.

The bookmarks are store in a file in you Profile folder, you can enter [about:profiles} to find where the profiles are. Then open that folder and you may find your bookmarks file. Then use a facility to open and read it. If there is nothing there then it is likey to have been overwritten.

You may have more that one Profile so check each, and if you find the bookmarks file move it to the profile you are currently using.

Please also see my response to the same question just before yours which explains some options.

https://support.mozilla.org/en-US/questions/1581741#answer-1818468

Thank you Amoun for your information & advice. I will try to follow your comments but am happy to say I'm still a novice at all this, even if 85. Cheers, Peter H.

85 is impressive