Do you mean the new tab page, that doesnt show bookmarks, it shows most visited sites. If you need to see your bookmarks, open the bookmarks sidebar (Cmd + B) or go to The firefox button/Bookmarks to see your list of bookmarks.

If you need history hit (Cmd + H) or go to Firefox button => History.

• "Most Visited" and "Recently Bookmarked" and "Recent Tags" are examples of so called Smart Bookmarks folders and are not real existing folders.
• Such smart folders show a list created by a query of the places.sqlite database that stores the bookmarks and the history in Firefox.
• Smart folder lists show a maximum of 10 entries by default.
• Bookmarks or history items that show up in a smart folder list are stored elsewhere in another folder and any changes made are applied to the real bookmark or history item.
• If you remove an entry then the list is shifted up and a new entry that wasn't shown previously is added to show 10 entries.
• If you add a new bookmark or visit a website then a new item is added at the top and the entry at the bottom disappears from that list.