What the others are trying to say in a nice way is that the other three plugs are directly under the coil packs on the side you did not do and do not require wires but do require you to unbolt the coil packs. (those things that the three wires you replaced plugged into). Hopefully this helps you out. Unless of course you have the 4 Cyl then you may just have to look a little closer to the firewall to find the fourth.
Hopefully helpfull even if a bit tongue in cheek on the tone.