There are at least three reasons why this question is moronic. First: If you've played Pokemon before, you would know that the last bit of information is unnecessary. A Moon Stone does the same thing to Eevee as it did in RBY, GSC, RSE, DPPt, and BW: Nothing. Second: If you actually had Pokemon FireRed in front of you, you would be able to select the Moon Stone, and Eevee would have "UNABLE" next to it. If reason two doesn't apply, refer to reason the Third: You clearly don't have Pokemon FireRed in front of you, so WHY are you asking this?
a59 Nothing happens when you use a Moon Stone on Eevee.