Dead Macbook battery

throwaway21

I received a work laptop maybe 4 years ago now and stopped using my own personal/college Macbook Pro that I had for about 5 years up to that point and had been working fine. After about 6 months I tried to start it again but the battery was probably completely flat at that point. I didn't mind too much as I could use my work laptop anyway.

It's come to a point where I want to find something from the older laptop. What's the best way to do this? Is there a way too reboot the battery/replace it or can I extract the contents of the hard drive some way?

should work just on charger if the charger and charging port is still working