Newer version of Firefox (Firefox 4 onwards) sports a cleaner Firefox button instead of the Menu Options. Apart from serving as a visual treatment, Firefox Button also provides quicker access to common tasks like Print, Save Web Page, Add-ons, History, and Bookmarks etc.
I personally like this layout, but if you prefer to Unhide the Menu bar in Firefox here is a quick guide.
There are three methods by which you can unhide the Menu Bar
1: Click on Firefox Button > Options > Menu bar as shown in the image.
2: Right Click anywhere above the browser address bar (Location bar) and select Menu Bar.
3: You can temporarily unhide the Menu bar by pressing the “Alt” key. The Menu bar will automatically hide when you click anywhere in the browser.
Getting the Firefox Button Back
You can use following methods to restore the Firefox button and hide the menu bar.
1: Click on View > Toolbars> Menu Bar.
2: Right click anywhere above the browser address bar and uncheck Menu Bar