The center is the midpoint of the diameter. So, center = ( (-2+6)/2, (-4+3)/2) = (2, -1/2)
The radius is the distance from the center to any point on the circle.
So, radius = √ [(6-2)2 + (-4+1/2)2] = √(16 + 49/4) = √(113/4)
Equation of circle has the form (x-h)2 + (y-k)2 = r2, where (h,k) is the center and r is the radius.
Equation of circle: (x-2)2 + (y+1/2)2 = 113/4