RealFlight G3 was sold as a package with the InterLink Plus controller and required it in order to work.
RealFlight G4 was sold as a package with the InterLink Elite controller and required it in order to work.
RealFlight G5 and later worked with both those InterLink types (as well as other new controllers as they were developed).
If you have RealFlight G3 but only an original InterLink (which is what the -IC- indicates), then it wasn't a legitimate sale, unfortunately.
I suggest you check out RealFlight 9.5S! The software has come a long way since G3 in terms of features, content, and refinement.