It's not about file formats but about physical meaning.
*SPICE is a "familiy" of time domain ( transient) simulators.
S parameters are obtained (measured or calculated) in the frequency domain assuming sinusoidal steady state (just the opposite of transient).
If your circuit is passive (vg. a PCB simulation using Momentum) , there are software out there that can synthesize an RLC network from an S parameter simulation. It is not trivial, there is an infinite number of networks that can be syntesized for a given S parameter set.
Good luck and study harder