Each college has different score requirements for the ACT. You can find these score requirements by visiting school websites and looking at admission profiles from the previous years.
However, you shouldn't look at the average or median score for a school and make that your "goal" score. If your score is the median value among applicants, this means that 50% of the applicants scored higher than you did. This should demonstrate how the median or average is not a very "safe" as a score to have in applications.