Which oxygen sensor tells the catalytic converter needs to be replaced?

This would be oxygen sensor #2 bank 1. here is a guide to help you walk you through the replacement and the location of the sensor for your car in the diagrams below:

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.