I need to replace the bank 1 sensor 1 on my 02 ES 300 and am having trouble figuring out which part to buy. Used the search function, but have not been unable to determine what I need. I'm taking it to my mechanic tomorrow and want to make sure I bring the correct part. Have it narrowed down to these two. If someone could tell me which one is correct it would be much appreciated.

Air Fuel Ratio Sensor

Engine: V6 (3.0L) CC: 2995 Part #: 234-9042) Position: Upstream Front

Engine: V6 (3.0L) CC: 2995 Part #: 234-9047) Position: Upstream Rear

 

bank 1 sensor 1 = Upstream Rear