HI kmshah423,
I told you just connect 9v to motor sheild and then to the Vin on the Arduino, make sure you connect all common/ground points. Do they still make carbon-zinc batteries their petty useless TOO! As I said you need lots of current to drive the motors, they will perhaps move with less volts as that's not what makes them work, it current, big batteries or a few good one's..
Mel.