I recently had my computer serviced by Geek Squad (never again) and they deleted my firefox.exe and all my bookmarks. When I browsed to C:\%APPDATA%\Mozilla\Firefox there was nothing there except a thumbnail of my old desktop background. I tried using the file recovery tool Recuva on the C:\%APPDATA%\Mozilla\Firefox directory but it came back with no files. I ended up reinstalling Firefox. Is there any way I can get my old bookmarks back?
Since you have a .json file you can open the bookmarks window and go to import and backup, restore, and choose your file. Note that this will overwrite anything new you've added. Remember to setup sync or otherwise backup your profile encase this happens again.