Please see below.
Work Step by Step
To plot the point $(r, \theta )=(-1, \pi )$, begin with the $\pi$ angle. Because $\pi$ is a positive angle, draw $\theta = \pi$ counterclockwise from the polar axis. Now consider $r=3$. Because $r \lt 0$, plot the point by going out one unit along the ray opposite the terminal side of $\theta$.