The period is 5. Start at x = 0 and trace the curve until you reach the same height as when you were at x = 0 (which is y = 3). The function repeats itself over again once you get to x = 5.
The amplitude is 2.5 since it is half of the vertical distance from the peak y = 3 to the valley y = -2. This distance is 5 units, half of which is 2.5