The satellite is in an
orbit. It will return to the lower elevation unless corrected.
To calculate the correct speed for the circular high orbit, set the expression for the centripetal force in the circular orbit equal to the gravitational pull of the Earth.
Compute the kinetic energy the satellite would have if it moved at that speed.
To get the energy
the satellite needs, subtract the kinetic energy the satellite has when it just reaches the GPS altitude in its elliptical transfer orbit.
If you need more extensive hints, step through the