how to find impedance of inductance with square wave input
Form the context of your question, it sounds like you are asking for an impedance magnitude in ohms. The problem is that this is only defined at a single frequency.

As a square wave is composed of a fundamental frequency, plus 0.33 3rd harmonic, plus 0.2 5th harmonic etc, you can make a good stab at an effective impedance (depending on how you want to define effective) by simply using the fundamental frequency.

If you want to define an effective impedance as (perhaps) rms voltage divided by rms current, then there are several ways to arrive at that figure, from analytical, to simulation with SPICE. The latter might be easiest, and also illustrate to you what happens to the waveforms (hint, the current wave is not square).