Main building.Connect 480 volt to 120/240 volt transformertto legs A andB of the 3 phase line. Next building connect another 480 volt to 120/240 volt transformer to legs B and C. Run just legs A and C to the third building (office) and connect up another 480 to 120/240 volt transformer there.
Tornado victims: Do not rush to rebuild. Take your time and look for and get a good contractor. Or consider selling the property and moving to a home that is ready to live in.