On a Firefox desktop version you should be able to restore the bookmarks from a backup in the bookmarkbackups folder.

• https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them

Hi Thank you very much for your answer. I tried the procedure on both the new desktop and the old laptop and the only backup available is from a 2 days ago when I downloaded Firefox onto the new device, that's to say the same Google bookmarks. Is it some kind of virus do you think? When I opened the old laptop just now the desktop window image had changed and there were pop ups on the screen.