Engine will not start Catalytic Converter was stolen?

We need to start by running the codes, here is a guide that will help:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If the catalytic converter has come apart it will clog the exhaust system, this will keep the engine from starting as well. I would lift the car up and use a rubber mallet to rap on the exhaust system to see if you hear anything rattling around inside the muffler and cat.

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

Please run down these guides and report back.

Okay so it's throwing 2 codes. P0037 and P0138. Again, I think the catalytic converter is probably not the best but what do you guys think?

Heater Control Circuit Low (Bank 1, Sensor 2) and P0138 stands for O2 Sensor Circuit High Voltage (Bank 1, Sensor 2) So for sure the post catalytic converter oxygen sensor is bad. I would replace the sensor first to see what happens. here is the location of the sensor and how to change it out in the images below.