Sensor 2 is usually after cat, AKA 'downstream'.

Bank 1 is cyl 1-3, bank 2 4-6

HOWEVER, I just pulled that up with 30 seconds of google. Use at your own risk. Honesly google yourself or call a parts counter (or ping the company that is selling you the sensor) for your own info.

And...O2 sensors are a wear item. Buy both, replace both. Good for another 60k -100k