Since the State Police use the MPSCS statewide trunked system, the "frequencies" would depend on which sites you would be monitoring (those closest to you).
Not sure what you mean by MPSCS "Codes".
Look for the control channels on the sites for the county/counties you want to monitor. Then note the MSP talkgroups used in those areas, keeping in mind that MSP might be dispatched by a local dispatcher.