Arduino Gameboy & MIDI Communication

Hello there. I am in the process of building a LSDJMC2 box from firestarters design and I stumbled upon your Arduinoboy! Nice! i was hoping for that. infact i thought about doing that before i decided to make the LSDJMC2 but thought that it would be too hard to code.

So i cant find much info on how to actually wire the gameboy cable into the arduino....
I bought some gba link cables and there are only 3 wires init even though it has 6 pins in the connector (and there is some copper shielding which i pulled back) .

How would i then wire this to the arduino?