Hello Patel!
Take good care of that old keyboard! The sounds were special in that time!
To record your songs to computer do this:
1. Download the free program Audacity.
2. Use an audio USB interface to connect your computer to the keyboard.
3. Record your music into Audacity.
I see you work with MIDI, so you may have more knowledge about these things then I. I also have an old keyboard, and intend to record some music from it. The demo songs in those old models were great, so record that as well
If you meant record MIDI to computer from an old keyboard, there are some gear for that as well, but here I am out of knowledge, as I only use Audacity

Have fun

Greetings from Trondheim, Norway.