Lost menu button and bottom bar for accessing softwares

Help, somebody, help,

I have lost the menu button (start button, well it was a LM button since the pc is running linux mint) and I can not reinstall it even by right-clicking on the desktop. If I right click on the desktop I do not get "settings" ....
hummmmm, what do I do ? restart the beast ? well "force-quit" and then start again ...????

:s

Thanks for your help
Joelle