Where is the bank one O2 sensor located on a 1998 Toyota4Runner? on 1998 Toyota 4Runner

I had a reading done on it that stated a bad O2 sensor, bank one

Asked by for the 1998 Toyota 4Runner
Depends on which engine you have! 4 or 6 cyl.???? V6 pass. side is bank 1, 4 cyl only one bank so it is #1. Now, is it sensor bank one sensor 1 or bank 1 sensor 2?? We need the actual code number(s).
4 cylinder
There is only one bank but two sensors! Sensor #1 is at the engine, sensor #2 is behind the cat. converter. Post trouble code(s).
It read "Bank one, sensor one".....that's an upstream sensor, right?
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bank 1 is the engine side that has number 1 cylinder.