The easiest way to find out what replacement capacitors to buy is to find the original capacitor datasheet.

Sometimes you can find capacitor datasheets by going to a company website. You can find some capacitor company websites here

The badcaps forum is also a good place to find information about capacitors.

When you get the datasheet, look at the provided information on diameter, length, ripple current, and ESR (for low ESR capacitors).