If you're not migrating the old Mac to the new one (the easiest way to keep all your preferences and settings), you can still get the Firefox bookmarks onto the new Mac. Open the Bookmarks Manager in Firefox (Bookmarks menu --> Organize Bookmarks) and select Export from the File menu. Save the Firefox bookmarks to a disk and then use the Import option on the same menu in Firefox on the new computer to add the bookmarks to Firefox or locate the bookmarks file on your new hard drive and replace it with the saved file. In Safari, select Import Bookmarks from the File menu.
Claire