You will need to find a black light that is found in the Belmont Park Box.

Find the turtle, jellyfish, and fish symbols with the black light in the seaworld area.

Using the black light in the bathroom, count how many of each symbol appear on the walls. There will be 8 turtles, 5 jellyfish, and 6 fish. 856 are the last 3 digits of the phone number.