probability that six students arrive in random hour

A statistics professor finds that when she schedules an office hour for student help, an average of three students arrive. Find the probability that in a randomly selected office hour, the number of student arrivals is six.

would my p=1 which repersents 1 hour in 24 and x = 2, please help

This looks something like a poisson distribution.

\(\displaystyle \L\\\frac{3^{6}e^{-3}}{6!}\)