Hi, thanks for requesting me. If you're trying to record your performance, midi isn't the way to go. Let's take a look at your options.
In Pro Tools, go to your setup menu, and select I/O. Click the input tab, and make sure your M-audio is selected to input channel 1-2. Connect PC88 audio out to M-audio inputs. Create a new stereo audio track, arm the track, hit record, and play something.
If M-audio isn't showing up in your I/O settings, your M-audio isn't compatible with Win10, or the drivers are not installed. To work around this, use a dual 1/4" male from your keyboard's audio out to your 1/8" mic input on your computer. Be sure your computer's sound card is select in your I/O settings, and you should be able to record on an audio track.
If you still have trouble, connect midi in to midi out/ vice versa. In your midi settings in your setup menu, select your midi interface, and be sure it's set to channel 1. Now, when you go to create a track, don't select an audio track, you want an INSTRUMENT TRACK. That is what you use for midi. You'll need to assign a virtual instrument to your plugins to hear any playback. Midi doesn't contain any audio, only commands to play a virtual instrument.