If for some reason the Firefox installed on your system does not show Menu bar as shown below, then you can unhide the menu bar by the
1. By pressing Alt key on the keyboard, navigate the Menu bar, Click on the
View menu –> Toolbars and tick Menu Bar from the menu list.
2. You can reset toolbars and controls by starting Firefox in Safe Mode.
Click on the Windows Start –> All Programs –> Mozilla Firefox –> Mozilla Firefox (Safe Mode). The following Firefox Safe Mode window will be displayed.
Select Reset toolbars and controls and click Make Changes and Restart button to apply the changes to Firefox.