Reading the codeS2M-200-6 is a S2M belt with a 200mm pitch length and a 6mm width. The S at the front tells you it’s the Supertorque profile.
Counting teethPitch length divided by 2mm gives the tooth count, so a 200mm S2M belt has 100 teeth.
Supertorque or HTD?An S2M belt has the same 2mm pitch as an 2M HTD belt, but the teeth are shaped differently and need S-profile pulleys. Replace like for like; if the old belt has no S in the code, it’s probably HTD.