How many O2 sensors or on the 2007 MKX?

What is your question?

Code shows O2 sensor/catalytic converter error. I checked on line to see how to repair the issue. On line it said there were 2 sensors, however, the auto pairs staff said there are 3. I wanted to know for sure before I change the 2 upfront and find that I need a third. The auto parts staff wasn't sure of the location of the rear sensor and could find it and gave a guess as to where it might be.