4/3(pi)r^3 put in the radius
4/3(pi)(6)^3
4/3(pi)216
864/3(pi)
That's your exact answer, or you can multiply by pi and aproximate the solution
$${\frac{{\mathtt{864}}}{{\mathtt{3}}}}{\mathtt{\,\times\,}}{\mathtt{\pi}} = {\mathtt{904.778\: \!684\: \!233\: \!860\: \!452\: \!7}}$$
Or about 904.8 cm