Hi, and welcome. The crankset/chainrings likely do not need replacing, but it is possible that you need a new chain and cassette. Any 6/7/8 speed chain will work, and any 8-speed cassette will work. I personally like the KMC X series chains (X8.93 or X8.99 for your application). Shimano and Sram both make cassettes will work interchangeably. Choose based on price and availability.