iMac PowerPC G4 (OS X 10.4.11) migration to new iMac Intel Core i5 (OS X 10.7)

I have a iMac PowerPC G4 (OS X 10.4.11) and want to migrate my files over to my new iMac Intel Core i5 (OS X 10.7). I have a FireWire 800/400 cable. Is this the correct cable? Migration assistant doesn't seem to p/u old HD but it shows on desktop of new computer. Am I doing this correctly? I can't get past where the migration assistant is looking for computer.