as salam alaikum
There is no fixed number to establish a mutawatir narration; rather mutawatir narrations are those narrations whose number of chains of transmission denote certitude. It is possible that a particular tradition may denote certitude with a particular number of isnads but another tradition may need a different number of chains. Some scholars put a fixed number of isnads in order to establish the tawatur, so it depends on the criterion that the scholars use and accept.
A mutawatir narration is a report whose truthfulness cannot be rejected due to its degree of certitude; therefore it does not depend on its availability on Shia or Sunni books. However one example found in both Shi'i and Sunni books is the prophetic hadith: "Whoever lies about me deliberately, let him takes his place in hell".
With prayers for your success.