Code P0420 bank 1, where is the catalytic converter located?

Yep! The catalytic converter is not good, here is the location and how to swap it out. Also, only the bank one cat is bad, but you should replace both but if you need to save money you might be able to find one for just the bank one application. Here is the location of the bank one cat: Closest to the firewall, right side of engine. Check out the images (below). Let us know how it goes.

Is bank 1 always on the side of the engine with #1 cylinder? So that would make rear catalytic converter related to back 1 sensor?

Correct, I gave instructions to change the catalytic converter on the right side of the engine, (bank1). All of the codes are for bank1 not the rear cat.