Which line to disconnect to drain transmission?

Hi everyone, been lurking here for years!

I was going to tackle the transmission fluid change (full tranny oil change). I wanted to know which line on my tranny oil cooler (2010 Tundra DC 4.6L with Tow package) to remove that will drain the tranny out once the engine is started.

I have a good sense of what I need to do but I don't want to drain the tranny from below the truck since I'm not going to be jacking it up (gotta be level to fill it properly).

This shot was taken in front of my radiator on the passenger side where the ATF cooler is. My understanding is that on the 2010 model year that toyota did a ATF cooler change and is now integrated into the rad or a/c condenser. I know for SURE i have the tow package b/c I have the tow haul button and tranny temp gauge on my truck.

Does anyone know what hose diameter I should be using to hook up to the cooler's output/return line?

Thanks!