1993 Jeep Cherokee leaking in the back passager floor board

The floor pan is designed to channel water to the rear, the drain requires you to get under the jeep, at the firewall on the passenger side, where the A/C evaporator case meets the firewall, you will find the drain. Clear it with compressed air, or carefully with a piece of wire, Peel the rug back and remove the rubber drain plug to help get rid of the water back there.