VERY old MIDI Drum PAD with PC

Well I am afraid that it is a piece of test equipment that might cost you a lot of money

However without one you will struggle to do any electronics.
You can make one with a laptop and an arduino. Just google arduino oscilloscope, for lots of designs.
These will let you see signals coming out of your pad. Unfortunately for you because this is so obscure unless you can get data on it you have to investigate and it is not the sort of thing a beginner is capable of doing. Spend a year doing electronics and stuff and then come back to your project.