You'll either have single licenses controlled with hardware keys on individual machines or some kind of network license.
To know the individual licenses, hunt for those protection keys attached to machines - they look like USB flash memory modules.
Also, the help menu of each machine with a running ArchiCAD will have a "Check for Updates" button that uses the internet to see whether your version of ArchiCAD is current.
I can assure you that since ArchiCAD 10 is already out, that you can answer this all with a single call to your ArchiCAD reseller for an upgrade quote since HE'LL know what your firm already owns.
Dwight Atkinson