Using MicroKORG as Midi controller

Hi, I recently bought a MicroKORG synth and a cheap Midi to USB cable for my iMac (2011 model). I want to be able to use the KORG as a MIDI controller on garage band but am having trouble doing so.

I plugged in the in and out midi cables into the korg and the usb into the mac and Garage band recognises it and tells me that there is 1 input avaliable. But after this there is nothing. I cant hear the sounds from garage band at all and there is no sign of garage band recieving anything from the KORG.

I have changed the Microkorg MIDI settings but i cant get it right. Any help would be greatly appreciated. Thanks 🙂