Under normal operation, the highest pressure in your piping downstream of the pump will be based on the pressure drop through the piping (which since it is short should be minor) plus the downstream vessel's maximum operating pressure.

If there is a valve in this line, which there almost certainly is, you also need to look at the case when this valve is closed and determine the maximum shut-off pressure from your pump.  Different companies have different ways of doing this, some assume the upstream/suction vessel is at its relieving pressure, others use the maximum operating pressure, etc.  This calc will decide what the piping upstream of the block valve needs to be designed for.