Answer
$3$, $\pi$, $-\frac{\pi}{4}$.
See graph.
Work Step by Step
1. Given $y=-3sin(2x+\frac{\pi}{2})=-3sin[2(x+\frac{\pi}{4})]$, we can find the amplitude $|A|=3$, period $p=\frac{2\pi}{2}=\pi$, and phase shift $-\frac{\pi}{4}$.
2. See graph.