The following equations should help:

Determine the volume of fluid you need for both hydraulic cylinders to extend and retract.

Flow rate: Q = D (Displacement) n ( revolutions) / 1000

Next, Horsepower Required to Drive a Pump from the GPM needed based of extending and retracting the cylinders and the pressure required

GPM x PSI x .0007 = horsepower needed

Next the Pump Output Flow (in Gallons per Minute)

RPM x Displacement ÷ 231 = gpm

Pump Displacement Needed for GPM of Output Flow

RPM x Displacement ÷ 231 = gpm