1. "Sto lat" - This is the most common and direct translation. It means "one hundred years" and is often used in the context of a birthday wish or anniversary.
2. "Wiek" - This means "century" and is more appropriate when referring to a period of 100 years in a historical or general sense.
So, the correct way to write "100 years" in Polish would be "Sto lat" if you are referring to a specific period of 100 years, such as an anniversary or a person's age. However, if you are talking about a century as a period of time, you would use "Wiek."