The codes have the format Pxxxx, e.g. P0420, which is a typical code for a catalyst problem.
Another thing: those codes do not say directly that a particular part is bad.
In this case P0420 says that the converter is not working efficiently.
It could be that the O2 sensors aren’t working properly (but not bad enough to set their own code) or the gases going into the converter aren’t correct (garbage in - garbage out) due to an exhaust leak or other issue.
If there are multiple codes then the lowest number code should be dealt with first, the higher number codes may then go away on their own.
Example: a problem (like a vacuum leak) causing P0171may also trigger P0420.