That's a question usually ask by women, and quite a lot, but anyway...... The inner thigh is not a heavily muscled area by nature, but they certainly can be developed to their full potential.
Might suggest squats (a wide foot spacing), lunges (in place or walking) and step-ups. Even wide footing on some forms of the DL. Sumo squats and DL's come to mind, also. Some gym's have different type machines/cables (sitting or standing) which may also draw your interest.
Generally speaking, wrestlers practice scissors type training for power of the inner thighs. As do ground fighters and other forms of the martial art. Good Luck.
I seem to have good development on quads but looks very thin and one sided, want to bulk up the inners to look balanced, proportional...doing box squats now but not seeing improvement.
And I don't want to use the girly machines....value my man card, that's why I asked for alternatives.