The recent iPad models that I have used have their front camera at the middle of one of the shorter edges of the face of the screen. In particular, it is on the edge opposite the edge on which you attach the power cord.
Even if you happen to have a model with the camera in a different position, it should be easy enough for you to determine its location by waving your hand in front of the iPad while FaceTime is running.
I find FaceTime looks most natural if I hold the iPad in portrait mode with the power port on the bottom.