Water is leaking back to passering floor when ac is on were is the drain if any how to stop it

your evaporator heater core drain hole stopped up not allowing drain on outside.look under vechicle below firewall look for drain hole try up stopping it using shop vac with a small tube or rubber hose tape to shop vac hose try vacuum out debris stopping up drain hole.

Usually a sign of a plugged drain tube.
The HVAC box has a tube that drains the water onto the ground.
The tube should be at the bottom of the firewall near the passenger floor.

You probably have two different issues here.
The water on the floor is usually caused by a drain tube being stopped up. The tube is supposed to let the water drain out of the car and onto the ground. It should be on the bottom of the firewall or below the floor.
You would need to have the computer scanned for trouble codes to find out why the check engine light is coming on.

HEATER CORE AND AC EVAPORATOR DRAIN TUBE STOPPED UP ALLOWING AC CONDENSATING WATER OR SWEAT TO RUN IN FLOOR BOARD.OR LEAKING HEATER CORE WILL CAUSE WATER OR ANTIFREEZE IN FLOOR BOARD.

check your drain hose for blockage, if it's clogged up the condensation will leak into the floor

It may be a leaking A/C condenser my advise would be to take it to an Air Conditioned Shop to have it checked. Good luck

the ac drain is more than likley stopped up, they tend to get clogged with debri not allowing the condensation from the evap. core to drain properly, thus allowing it to leak into the floorboard.

clean out ac condensation drain,it is carring it around and pouring in the floor as it sloshis around

AC drain hose stopped up somewhere, probably under the vehicle. Sorry I don't know where it comes out of the firewall or fender.

it sounds like your heater core is busted. you will have to go under the dash to get to it and replace with a new one