Depends on the car but often you can see if when you open the hood and look behind the engine, in about the middle of the firewall. Sometimes you'll need a lift to see it as on some cars it's down low behind the engine. I'm pretty sure on your car you'll have to jack it up and peel back a heat shield to gain access to the drain hose.
There's a service bulletin about this if you want to do more research:
#09-01-37-002D: Water Leak into Front/Rear Passenger Floor and/or Carpet Wet (Inspect White Plug in HVAC Evap Drain and Apply Sealer to Front of Dash) - (Sep 27, 2010)
Subject: Water Leak into Front and Rear Passenger Floor and/or Carpet Wet (Inspect White Plug in HVAC Evaporator Drain and Apply Sealer to Front of Dash Area)
Comments
There's a service bulletin about this if you want to do more research:
#09-01-37-002D: Water Leak into Front/Rear Passenger Floor and/or Carpet Wet (Inspect White Plug in HVAC Evap Drain and Apply Sealer to Front of Dash) - (Sep 27, 2010)
Subject: Water Leak into Front and Rear Passenger Floor and/or Carpet Wet (Inspect White Plug in HVAC Evaporator Drain and Apply Sealer to Front of Dash Area)
Models: 2008-2010 Chevrolet Cobalt
2008-2011 Chevrolet HHR, Malibu
2008-2010 Pontiac G5
2008-2009 Pontiac G6
2008-2009 Saturn AURA