Press <Shift><Control> B to bring up the bookmarks window. At the top of the window is a button; Import And Backup. Select Export Bookmarks To HTML. When asked, give a folder and file-name to save the file.

Best way to do it is to backup your current bookmark so you can just import them on your new PC. To do this Click on your bookmarks button and select "Show all Bookmarks", or CTRL+SHIFT+B. That will open a new window. Once that window opens click on "Import and Backup" and select "Backup". It will bring you to a save window and you will a file name that will be "bookmarks-2014-XX-XX.json" with the XX representing the date that you save it on. Save that file to a flash drive or some form of external media and once you have your new PC you will be able to import your bookmarks by repeating the same process as above but instead of choosing "Backup" you will choose "Restore > Choose File" once you so a window will open and you will be able to navigate to the drive that you saved your bookmarks to and select it and voila you will have you bookmarks on your new computer.

See also:

• http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox
• https://support.mozilla.org/kb/restore-bookmarks-from-backup-or-move-them

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox