Hi,
After 4 years without being charged, most probably the battery has become depleted beyond recovery and would need to be replaced.
You could get a replacement battery but most probably it would need to be charged so you would need a charger to do this.
If you got a charger only, you may be able to use the laptop by removing the battery from the laptop and running it on the charger only.
Search online for ''693715-001'' to find suppliers that suit you best.