How can we calculate single phase to ground fault current knowing only the three phase fault and line voltage?
I believe they gave you phase-ground fault current (which is 3I0) to begin with. But, to answer your question:  No, you cannot calculate the phase-ground fault current if all you know is the system voltage and the three-phase fault current.  You can guess, and assume the zero sequence Thevenin impedance equals the positive and negative, but that is guessing, not knowing.