Answer
Sphere centered at the origin with radius $3$.
Work Step by Step
Conversion of rectangular to spherical coordinates is as follows:
$x=\rho \sin \phi \cos \theta; y=\rho \sin \phi \sin \theta;z=\rho \cos \phi$
and
$\rho=\sqrt {x^2+y^2+z^2}$;
$\cos \phi =\dfrac{z}{\rho}$; $\cos \theta=\dfrac{x}{\rho \sin \phi}$
Here, $\rho=3$
This implies that $\rho^2=9$
or, $x^2+y^2+z^2=3^2$
Thus, we have the surface of a sphere centered at the origin with radius $3$.
