you wont find the dipstick because there isn't one. you have a sealed GM4L30E transmission. Jack up the car level. Locate the rear transmission pan. You'll see a drain plug (lower, pass side) and a fill plug(higher up on the drivers side. 17mm wrench undo's the fill plug. Dont undo the fill plug unless the car is running and at normal operating temp. Cold, engine stopped, unscrew the fill plug = transmission fluid all over the floor. So, when it's hot and running pump dexronIII into the fill plug until it dribbles out the side. It is now at the correct level.