COM ports can and do change, so there isn't a port number I can give you. But the system should handle all of this automatically for you. If you are having trouble, unplug any USB cables, go to the Serial Ports dialog and touch the "Reset to Defaults". This will set any ports listed to "Do Not Use", except COM2 which will be set to the internal GPS. Now, any USB serial ports that are attached to your iFly will show up as "Auto Detect". This is the desirable state.
Hope this helps,
Walter