Answer
See below.
Work Step by Step
$x^2+y^2=6y+16\\x^2+y^2-6y-16=0\\x^2+(y-3)^2-9-16\\x^2+(y-3)^2=25=5^2$
The general equation for a circle with radius $r$ and center $(h,k)$ is: $(x-h)^2+(y-k)^2=r^2$, hence here the center is: $(0,3)$ and the radius is $5$.