Hi everyone! I am trying to get my car fixed and get the check engine light to go off!

I have a 2004 Dodge Intrepid 6 cyl. with 2.7 L engine.

I took it to auto zone and the code they gave was P0138.
It says bank one sensor 2.

I can see all 4 sensors when I look under the hood. I need to know if this is the sensor on the drivers side or the passenger side, and also if it is the sensor on the top of the engine, or the bottom. I am not really that familiar, so if when ppl say it's the upstream or downstream or whatever, I have no idea what that is. I just need to know which side, and is it top or bottom, lol.

Also, when I order it, what kind do I need to order. They had all these listings for different ones, such as, heated or unheated, replacement or non replacement, etc.

Please help a damsel in distress (haha)