where is the oxygen sensor located so I can replace it? on 2000 Lexus RX300

I wish to replace the sensor. where is it located in the engine compartment or elswhere?

1 answer 2 comments
This vehicle will have at least 2 and maybe 4 sensors. Do you mind if I ask, "Why are you replacing the sensor?", is there a check engine light on? I ask because the oxygen sensor replacement is often not needed and is often mis-diagnosed, even by experienced mechanics.
engine light diagnosis says bank 1
you are not answering the question, if there are 2 - 4, where are they located please.