after a while it opened only six and showed a message: "Unable to process the backup file".

I wanted to import Firefox bookmarks saved as json file, on my new computer (windows 10), Firefox version 61.0.2( 64 bit.) (Old computer was 32 bit). When I opened Firefox/Bookmarks/Show All bookmarks/Import and Back up/Restore/Choose file after a while it opened only six and showed a message: "Unable to process the backup file". I have also tried Session history Scrounger For Firefox (drag and dropped the json file) but nothing. What does this means "Drag and drop one session history file" one session I did not get it? https://www.jeffersonscher.com/res/scrounger.html If there is any way to open that json file or import boo marks in to Firefox that will be great, please suggest the solution and oblige. Thank you Ari94