you will need more data than just the TDH
the three points should bracket the point of maximum efficiency of the pump. If you are specifiying the pump, you should also bracket the minimum, maximum and average design flows expected in your system. Therefore, assuming you are pumping into a transmission main which is interconnected with your distribution system,
Point 1 - low demand, high system pressure
Point 2 - average demand, average system pressure
Point 3 - high demand, low system pressure