Start with the formula of the volume of a cone
volume of cone = (1/3) pi * r^2 * h
Now you double the radius and the height.
The radius becomes 2r, and the height becomes 2h.
volume of cone = (1/3) pi * (2r)^2 * 2h
= (1/3) pi * 4r^2 * 2h
= (1/3) pi * 8r^2 * h
= 8 * (1/3) pi r^2 * h
As you can see, the volume became 8 times larger.
8 * 350 cm^3 = 2800 cm^3