They arent plugged into your motherboard. They are plugged into the fan controller via 3/4 pin connectors (cant remember which one). Behind the right hand panel you will be able to unplug all these. Unscrew the fans and install your new ones. Just plug them into the pins you just took the old ones out of.
The process is pretty easy, if your really stuck maybe you shouldnt be opening your case. Have a look at anti-static practices, and youtube should installing new fans to get a walk through. Remember these are case fans, not CPU or anything else, so they generally dont go onto the motherboard.