Have you looked at this firefox help link? "How to retrieve bookmarks from a dead computer." https://support.mozilla.org/en-US/questions/1003872

There may be glitches when transferring a Firefox profile among computers, but it's worth a try. If necessary, you can always use the old files for a more selective restore. '''Part 1''' First, set Windows to show hidden files and folders: https://support.microsoft.com/en-us/windows/view-hidden-files-and-folders-in-windows-97fbc472-c603-9d90-91d0-1166d1d9f4b5 Second, find the relevant profile folder on the old drive. For reference, I'll call it the "E" drive, but this would be whatever letter is assigned by Windows. Explore up E:\Users\<username>\'''AppData'''\'''Roaming'''\Mozilla\Firefox\Profiles That Profiles folder typically contains at least two subfolders whose names combine a random portion and a descriptive name like "default-release". The immediate objective is to identify the most (recently) used profile. You can use the Last Modified dates and/or double-click into the '''bookmarkbackups''' folder to see whether it has up-to-date backups. The file creation dates are embedded into the file names, for example: bookmarks-2024-11-22_2498_''gibberish''=.jsonlz4 Got it? '''Part 2''' The idea is to transplant the entire old profile folder (not Profiles, just the individual folder) into the same location on the new PC. Then you need to educate Firefox that it's there. The following post has the steps (with a different source folder): https://support.mozilla.org/en-US/questions/1474421#answer-1687884