Your chain became so worn out from use that it ruined one or more of the sprockets of your cassette. You may also have damaged one or more of your chain rings.
Unless you have a Campagnolo rear hub, you just need to source a cassette with the same number of sprockets. This is also an opportunity to tweak your gear ratios if you want, so long as you don't exceed the tooth difference capacity if your rear derailleur. If you never use your current lowest gear you could, potentially, fit a cassette with a smaller largest sprocket. This will give you a higher bottom gear, but give you more gears in the range you tend to use. If you currently have a 13t smallest sprocket, opting for a 12t or 11t would deliver a higher high gear. If in doubt, simply replace your old cassette with a new one with the same tooth numbers and it'll work as its creator intended.
Every 'Shimano compatible' cassette will work whether SRAM, Miche, Shimano or any of the many off brand cassettes you'll find on
ebay.
