Return tranny line

I have a new tranny cooler for my auto and I have searched all over and I'm not getting anywhere. Some say top line is return some say bottom. Can someone let me which one it is??? please

I'm not sure if this is correct but shouldn't the trans fluid go through the radiator in the oppisate way that the coolant flows to cool it?

Is it correct to say that the bottom line should be the return to the transmission?

I have used the search function on many forums but they all say different things.

Thanks Ram