Answer
The Amplitude is $ \frac{1}{3}$
The Period is $ 6\pi$
See graph below.
Work Step by Step
For
$y=a\sin c(x−h) + k$ $y =a \cos c(x−h) + k$,
Amplitude: $|a|$, Period: $\frac{2\pi} {c}$,
Given $y = -\frac{1}{3} \cos (\frac{1}{3} x)$
The Amplitude is $|-\frac{1}{3}| = \frac{1}{3}$
The Period is $\frac{2\pi}{\frac{1}{3}} = 6\pi$
The transformations are as follows
The blue graph represents the graph of $\cos x$
The red graph represents the graph of the given function that is reflected about the x-axis, compressed horizontally by a factor of 3 (calculated by $\frac{1}{c}$) and stretched vertically by a factor of $\frac {1}{3}$
See graph below.