You need three things:
1. An XLR cable. Also known as a mic cable. Most facilities have them, but I keep a short 3-foot one with me just in case. You can get this
at any musical instrument store. Price varies depending on the length.
2. A DI box. These can be purchased anywhere guitars are sold - Guitar Center or you local mom and pop music store Costs around $30.
3. A stereo iPod cable with an 1/8th inch male plug on one end (standard iPod plug) and a quarter inch male plug on the other (this
goes into the DI box). You can get this cord at Radio Shack. $10.