What will be the cable size for 250hp Fire Pump, Power Supply: 415 Volts, 3 Phase

If this is homeowrk look it up yourself and tell us what you got. We will not do your homework for you, but we'll certainly discuss your findings.

If this is a job ask your foreman. If this is a job like this and you are coming here looking for answers on how to do it that is sad.