What controller do you need to play gamecube games on wii?



I got a wii system. I also got a Classic Controler. I just got a gamecube game and the right kind of Memory Card. But when i first start playing the game. (using the classic controller)
It dosn’t work. And my wii remote turns off. What kind of controller or what exactly do I need to play gamecube games with a wii and where do I put it in? PLEASE HELP I REALLY NEED A ANSWER!!! thanks!