Are you moving from AMP1, AMP2 setup to a combined AMP1? Or are you moving the data from AMP1 + AMP2 into a new AMP3?
In either case, are the buildings on both AMPs the same, completely different, or some shared/some new? And is floor plan/AP placement the only portion you're trying to save?
Based on the answer to the above, the response would be significantly different.
The easiest:
Assuming you only care about VRF data and moving from AMP1 + AMP2 to a single AMP1:
From AMP2 - navigate to VRF, drill down into a campus, right click on a building, export floor plans.
From AMP1 - assuming controllers and APs have already been added, navigate to VRF, import tab, import from VRF backup.
And then you should have a combined image of both sets of floor plans.
If you only care about VRF data, and there's some mix of overlapping buildings, you might also try to load the VRF Planner on Windows or Mac. Then you can repeat steps to export from both AMPs and then import. This will mock up the above scenario as well. If you find you're missing some things, then the trick is to change the name of the campus prior to exporting. Then when you import, you can move buildings/floors between the AMP1 and AMP2 campus entities restored.