If coordinates of the center of the circle are (x0,y0) and radius of the circle is R then equation of the circle is such:
(x−x0)2+(y−y0)2=R2
In our case:
x0=5y0=−3R=6
Substituting this into circle equation we get:
(x−5)2+(y−(−3))2=62
Simplifying:
(x−5)2+(y+3)2=6