You can try this but I think there are too many differences between booth OMD versions that a simple “omd update” will work without problems.
But with the “omd backup” command you have the possibility to get back to the starting state.
What you need to do after the update command is, check the configuration that all Consol specific things are switcht of or better said not active (Gearman and so on)
The most important question before doing anything is - how was the Naemon configured.
I don’t think that the config can be migrated between Naemon and Nagios Core. But I’m not sure.
If i need to do a migration from some other monitoring with livestatus available, then i do an object export over livestatus and use this for the object creationg inside the CMK.