There are a few moving parts here.
1. You have hardware that isn't supported on newer code (which the 7200s need to run). These are the 800s and 2400s in your network.
2. Is this all under one master or pair of masters today?
There are a few ways to tackle this. What is your intended design? Once we know that , we can help in getting you there. The issue is that if you place a 7200 into an existing master local arrangement, it will require you to upgrade to a more recent code which isn't supported on the older controllers (800/2400).
So...are you replacing these controllers or are they staying for the foreseeable future? If they are staying, you can break them away from the master (if they are locals today) and then have them managed as their own islands.
As far as converting the config, this should happen when you upgrade the existing master to the latest code. You can add the 7200s as locals and once added, you can then flip the role to a master on the 7200 which will retain the configuration received from the "old" master. Then...you move your locals from the old master to the new 7200 master. There are some caveats to this and I would encourage tac assistance when you want to begin. Any questions though, please ask!