How many O2 sensors does my car have?

Your car has four oxygen sensors total, two primary and two secondary sensors. here is the location of the sensors and how to change them out. Here is a generic guide to help you step by step with instructions in the diagrams below to show you how on your car:

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Check out the images (below). Please let us know if you need anything else to get the problem fixed.

Your car has a total of 4 O2 sensors. There are two mounted in the exhaust manifolds before the converters, those control the fuel mix for the engine. Then there are two more mounted behind the converters, those are there to monitor the converters in operation. The upstream two would give you lean/rich codes while the downstream ones give the codes like a P0420 or P0430 telling you that the converters are not operating. However, in most cases people see the related codes and replace the sensors, when the issue isn't the sensors but the parts they monitor. That is why scan tools are needed so much these days, they can tell you what the sensors are "seeing" in the exhaust stream and let you test them some to determine what the fault really is.
Do you have a sensor related code?