A CPM is a Container Pallet Message for a containerised aircraft, be it narrow body or wide body. Its to allow the down route station to plan the offload.
The information you are looking for for positions 42L / 42R etc is for a CPM. I'm not sure if i'm understanding your question correctly or not however the information for these positions comes from the completed LIR / UWS ? Notoc etc.
Generally you will need the ULD number, the commodity type and the destination. If you need to put in the weight then it's the Tare weight of the ULD plus the weight of whatever is in said ULD.
I'm unsure of the software you are using but I'm sure that in some, for example ALTEA, if you produce an LIR in it then it will auto produce a CPM when the departure station departs the flight.
If you are sending a CPM then you should also be sending a UCM (Unit Control Message) for stock control purposes.
Hope this helps.