Don't worry, it's a common issue that can be easily fixed. Here are the steps to unhide the menu bar in Excel:

1. Press the "Alt" key on your keyboard. This will bring up the menu bar temporarily.
2. Click on "View" in the menu bar.
3. Select "Toolbars" from the drop-down menu.
4. Check the box next to "Menu Bar" to make it visible again.
5. If you want to keep the menu bar visible permanently, click on "Tools" in the menu bar, then select "Customize".
6. In the "Customize" window, click on the "Options" tab.
7. Check the box next to "Always show full menus" and click "OK".

That's it! Your menu bar should now be visible again. If you're still having trouble, try restarting Excel or your computer.