You do this exactly the same way as your other surface area problem. Recall the surface area formula:
!integral
$$f_y=2y, f_x=2x.$$
So we have $$S=\int_{-5}^5\int_{-\sqrt{25-x^2}}^{\sqrt{25-x^2}}\sqrt{(2x)^2+(2y)^2+1}dydx$$
Can you take it from there?
Alternatively, you could do this using polar coordinates, which is much easier:
$$S=\int_{0}^{2\pi}\int_{0}^{5}\sqrt{4r^2+1}rdrd\theta$$