Do you see your bookmarks in either of these places:

• Bookmarks Sidebar, either:
  • Ctrl+b
  • (menu bar) View > Sidebar > Bookmarks

• Library dialog, either:
  • Ctrl+Shift+b
  • "Show All Bookmarks"

Note: In the Library dialog, click Bookmarks Menu or Bookmarks Toolbar in the left column.

If you can see the bookmarks there:

You could have an issue with:

(1) Bookmarks Menu button is missing from the main toolbar

To get it back, try: Customize Firefox controls, buttons and toolbars

(2) Menu bar may be missing, or (3) Bookmarks Toolbar may be missing

To turn different bars on and off, you can use one of these methods to show the toolbar list and select the desired bars there:

• right-click a blank spot on the tab bar (or the "+" button)
• tap the Alt key to activate the classic menu bar > View > Toolbars
• in Customize mode > Show/Hide Toolbars (see: Customize Firefox controls, buttons and toolbars)

To turn on the Menu Bar, Bookmarks Toolbar, or other bars, click it on the list.

Any luck?

On the other hand, if your bookmarks are missing everywhere:

During a Refresh, your old profile folder storing your bookmarks, saved passwords, and history, moved to your Windows desktop inside a folder named Old Firefox Data. Can you find that?

Inside, click into the semi-randomly-named profile folder and then find a folder named bookmarkbackups which should contain some number of automatic bookmark backups with names similar to:

bookmarks-2016-08-24_2500_gibberish==.jsonlz4

In that example, 2500 is the number of bookmarks stored in the file.

You can replace your current set of bookmarks with one of those backups by following the steps in the following article. When you get to the restore menu, use Choose File, and direct Windows over to that folder on your desktop to pick up the old backup.

Restore bookmarks from backup or move them to another computer