macbook motherboard

Hello,

I have a macbook which I bought 4 years ago. Unfortunately last year it stopped working (connecting the charger to the laptop would not give any power to the laptop) and AppleCare told me that the motherboard was damaged. As the repair charge was quite expensive, and the laptop 3 years old I decided to buy a new MacBook Pro instead.

I have heard recently that it is possible to sell the old MacBook for parts. However, I am worried that all of my information is still on my old laptop (files, etc) and I have no way of removing it. Any info on this or suggestions would be greatly appreciated.

Many thanks!