So I noticed your keyboard has a 1/4" output jack, which got me thinking about hooking it up to an audio interface, and then treating it as a Line in to FL Studio in Mono. That way you’d essentially be able to preserve any sound you make on the keyboard over to a recordable audio signal that your DAW can process.
In simpler terms, you’d basically be treating the instrument as a microphone with an output that FL studio would be able to capture and record. The downside is that you would not be able to do any post correction (stuff like quantizing or fixing wrong notes) but it would preserve the sound as you hear it when you play just with the keyboard alone.
In order to do this you’d need to connect your keyboard to an audio interface via the 1/4" output on the back of your device and connect it to a USB Audio Interface that accepts 1/4" and not just XLR (which is the standard, if not you’d need a 1/4" to XLR adapter). If you’ve never heard of an audio interface before, it’s basically an external box that will transform digital data into analogue data or vis versa. You need this to connect to your computer so that you can record the sound that’s coming out of the keyboard, letting the data travel through USB into FL studio. It’s kind of like a more powerful and versatile external soundcard with more hardware and connectivity around it. They costs around $100 (but even if you don’t use them for this they’re very useful for live shows, and 100% necessary for XLR microphone to computer audio recording)
So yeah, though this method you’d be able to capture audio from your keyboard into FL, and technically you could record one note at a time as a .wav and use that to build your own personal Soundfont bank through 3rd party software like Vienna SoundFont Studio. HOWEVER, the reason I said this is crazy is because you literally have 500 different voices/instruments programmed into your keyboard, meaning that will you have to export 500 individual .wav files just for 1 single note on your keyboard and repeat ad nauseum.
It’s an incredibly ridiculous process, but that way you’d be able to port over every sound of your keyboard into a soundfont library, although I definitely would not recommend this unless you have some serious time to kill, or if are only a few specific instruments you wanted to work with. Unless there’s some way of finding an datamined bank online that has all the soundfonts your keyboard uses, or there’s a way to render and export audio files straight from your keyboard, I’m afraid you’re out of luck.
But hey you could save yourself a heck of a lot of trouble and money and instead just look for professional VSTs that emulate the sound you want. See if Yamaha sells any VSTs similar to the one’s pre-programmed into your keyboard and spend that $100 on something that will save you a lot of time and sanity. That’s my advice anyway