You might want to look at Firefox help here. It has to be done from the older computer to move to new computer.

https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Hi, markwarner22

     Thank you for your reply, appreciated very much. I will try and see if your help and instructions will do the trick. Please give me a little time get things together with my other computer to try and see if the bookmark transfer will work. I will get back to you with the results. Again, thank you markwarner22 for your help.

Make sure to us a USB drive so that the iOS will be able to read and import the data over.

Hi markwarner22,

   Thanks again for your reply. Your comment, "Make sure to us a USB drive so that the iOS will be able to read and import the data over." may be the reason I'm having trouble transferring my Firefox bookmarks to my iMac computer? I followed your instructions as per the transferring book marks and I'm pretty sure it was done correctly. But, I'm having difficulty in being able to transfer those bookmarks to my Apple computer? I see with the iMac OS it has a provision? to make that bookmark transfer. But, I just can't see those exported bookmarks with the Apple computer? Part of my problem may be I'm just not a computer wizard and I'm missing something I should be doing that maybe most might find elementary? Can you help and explaining use a USB port drive as you mention? Does that mean connecting a USB connector between both computers? I have never done what I'm trying to do, so I would appreciate your help and patience. Hopefully you can help my situation as I would like to use the later model computer I have acquired. Certainly appreciate your help and patience with a novice computer user. Thank you, markwarner22.

Hi Markwarner22,

   Let me explain what I have done so far. I sure I executed the export bookmarks from the https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer. I put the exported bookmarks to desktop like you suggested. The issue seems to be when I go to my iMac from the HP computer where the bookmarks were exported.  When I open Firefox in the iMac I go to bookmarks then manage bookmarks. I then go to import bookmarks from HTML. I then get a window, at the top of that window I see a library link, but there are other options also, like desktop and another half dozen options.  But, I then hit a stone wall after I click on either library or desktop. There's a link at the bottom that says cancel or open. I certainly would think I would want to open the open link, but that olption is not open, only cancel? Can you possibly explain what is happening and why I can't open either library or desktop? 
   I would appreciate your help, markwarner22. Can you help and explain why I can't seem to import my bookmarks from my HP computer to my Apple? Thank you, markwarner22.

Did you use a USB drive to store the data? And was the Mac able to see that data as well?

markwarner22,

     Thank you for your reply. I did install a USB flash drive when I executed the export bookmarks procedure. Little surprised if all those bookmarks were downloaded to that USB flash drive? But, what do I do now with that USB flash drive? Do I plug it into the UBS port on the iMac computer? Is that how the Apple computer "sees" those exported bookmarks, markwarner22? Appreciate your help. Thank you, markwarner22.

Can you edit your replies so they aren't scrolling text?

markwarner22,

  Sorry how the replies are being sent. I can see how that would be annoying!!! But, when I tried to remedy the problem, it seems I get a dozen fixes? Can you give me a simple one fix solution to change my replies from a scrolling text and are normal. Frankly, the way they used to be sent. Don't know how or when the change happened? Still would like to solve my bookmark issue once we solve this text issue. Thanks again, markwarner22.