How many O2 sensors are on a 1992 Chevy CK1500 with 4.3 V6 and where they located?

A 1992 Chevy CK1500 with a 4.3L V6 engine typically has one O2 sensor. It's located in the exhaust system, downstream of the catalytic converter. The exact location will vary slightly depending on the specific exhaust manifold and routing, but it will be fairly close to where the exhaust pipes join to become a single pipe after the catalytic converter.