The drain hole is behind the panel you removed in the metal pan numbered 7 in the pic below:
Right below that hole in the pan is the hole for the drain. The drain usually runs down from the freezer into the area labeled number 24 in the picture below. You may have to remove it to clean the drain out there. Make sure you stick something down into the hole and confirm that it is clear.
I hope this information helps you find your problem. Let me know if you have any other questions.
IS THAT PART #24 REMOVED BY REMOVING SCREWS OR IS IT SOMEHOW SNAPPED IN? ALSO DOES THAT PAN # XXXXX HAVE TO BE REMOVED TO GET TO THE DRAIN HOLE. ALSO, WHAT IS THE PART NUMBER OF THE DRAIN TUBE? THANK YOU.
SORRY, I WAS HELPING A FRIEND AT HIS HOUSE SO I DO NOT HAVE THE ABILITY TO LOOK AT IT RIGHT NOW.