Ty. Ok. If it's the catalytic converter, can I fix it? Is it expensive? And what do I need to do and get?

You can put a new one on(after-market) or remove it, at its age should be past any inspection. Can use a test pipe with a O2 sensor threaded port on it with a spark plug anti-fowler (drilled out some just past the threads to allow the O2 sensor end some space, just get the one that fits your O2 threads inside & same outside thread size as O2. Do not drill out the threads need them for the O2 to screw in, but carefully drill out the area past the thread for the sensor end it should not touch the interior sides of anti-fowler.. This will let the sensor work without setting on the check engine light. Or take off cat, take a pole/pipe/long screw driver ect and clean out the center of cat. You do not have to clean the entire cat out just the center the same size as you exhaust pipe, Shake out all the loose pieces & hook O2 back up and reinstall.

nothing to add, enginecreator covered it all.