Hey Richard, you said you want to record MIDI tracks into Sonar yet you are mentioning an old GTrack mic that you are currently using. Are you sure you are referring to MIDI track recordings or Audio recording ? They are two very different things.
Your keyboard has a USB to Host interface built in so you can use a standard USB cable from your keyboard to your computer, you'll need to download the yamaha USB drivers for your keyboard, once installed, select the midi interface in Sonar to be used (should be displayed as Yamaha USB). Create a midi track on Sonar, hit record and Sonar will record your keyboard's MIDI data. If you want to record the audio outputs of your keyboard to your computer then there are two ways.
If your computer has a built in standard audio card, they usually do and have a 3.5mm Line Input jack, you could get a stereo Y cable (Stereo Left and Right Male connectors to a single stereo mini connector) and plug your keyboard straight into your PC. The latency (which is a delay that can happen when recording using basic MME built in sound drivers) can occurr so you'd want to download the ASIO4ALL driver which will provide better performance for recording with a built in PC audio interface.
OR you could buy a dedicate USB Audio interface but it will need to have stereo inputs so you can plug the stereo outputs of your keyboard straight into the interfaces's stereo inputs. You'll be able to record the output of your keyboard straight into Sonar for audio recording of your keyboard.
Actually your GTrack has an instrument line level connector so you could plug a Y Stereo cable from your keyboard to the GTrack, I used to have one of these for vocal recording and hooking up a guitar fx processor to the line in.
Also, Sonar LE is very old software and recently in case you don't know, the Cakewalk company has been sold by Gibson and purchased by a company called Bandlab. If you register an account with Bandlab (which is free) and download and install their Bandlab assistant software (which is free), you can then download a new full pro level featured version of Sonar Platinum (minus some of the bundled plugins) for free, its a massive step up from Sonar LE. I recently downloaded this and its superb, so much better than my old Sonar X2 Studio software.
Hope this helps.
Justin.