Acini Di Pepe Pasta is a small round pasta used in soups. The name translates to "peppercorns" in Italian and describes the size and shape of the little pasta.
This little pasta is typically easy to find in your local grocery store or Walmart. Otherwise you can purchase it online at Amazon.com: De Cecco Acini Di Pepe
If you don't have acini di pepe pasta then one of these substitutes will work well: