Where is the ac drain line located exactly?

An exact location will be hard to define. But, It will come out of the firewall, passenger side, low on the firewall. You’ll see a black tube probably with an I.D. of 5/16th’s hanging straight down. What I’ve found to be most likely problem is the floor mat will get pushed up kinking it inside where it comes off the evaporator box. Could be debris has got into evap then has clogged it. It should be fairly easy to see from the passenger side floor. All else fails, take it off and blow through it. To get rid of the smell. I recommend using “Ozium” spray. Set your controls on Recirculate, low fan speed then spray it at bottom of evaporator box ( give it a good long spray). That way it will get sucked into evap core. Then shut it all down, let it sit for as long as you can. It will kill any bacteria. I’d give it a shot of it from time to time just to keep it clean. Hope this helps.