The volume of a cylinder is given by volume = pi*radius 2*height, so here we have pi*radius 2*36 = 9156.2, which we can rearrange to get radius = sqrt(9156.2/(pi*36)) inches:
$${\mathtt{radius}} = {\sqrt{{\frac{{\mathtt{9\,156.2}}}{\left({\mathtt{\pi}}{\mathtt{\,\times\,}}{\mathtt{36}}\right)}}}} = {\mathtt{radius}} = {\mathtt{8.997\: \!698\: \!748\: \!809\: \!832}}$$ inches