Most likely the evaporator is leaking going to be big bucks as dash and heater box have to come out.

your car has a tube that lets the water from the ac drain out. the tube is probably stopped up. have someone raise the car up and blow air into the tube from underneath. this will more than likely unstop it. water should pour out of the tube. if it doesn't, then you will have to remove that evaporator from the dash. but usually forcing air through the tube works. good luck.

I think it will be costlier to repair 1998 Air Conditioning System.....

under the dash on the right side and under my glove department its leaking water inside my car what is it and what do I do?

Buy some of this stuff, I have used it and it is great.