Answer
$(3\sqrt2,135^\circ)$
Work Step by Step
To convert from polar to rectangular coordinates we use $x=r\cos\theta$ and $y=r\sin\theta$. To convert from rectangular to polar coordinates, we use $r=\pm\sqrt{x^2+y^2}$, $\tan\theta=\frac{x}{y}$, but aware of which quadrant the point lies in.
Hence here the given point in polar coordinates $(\pm(\sqrt{(-3)^2+3^2},\tan^{-1}\frac{-3}{3})=(3\sqrt2,135^\circ)$
