It is hard to know this for sure because the genealogies of present-day individuals is not known for sure in all cases. Therefore, there cannot be any exact count of the number of "black Indians."
The tribe that is most likely to have the most "black Indians" is the Seminole tribe. This tribe originally lived in Florida and harbored many African Americans. Black slaves would escape into Florida and take refuge, in some cases, with the Seminole.
It is possible that your textbook or your instructor might say that the Cherokee are the tribe with the most "black Indians." The Cherokee had African American slaves and also had other contact with African Americans. Therefore, there came to be a relatively large number of Cherokee with African American blood.