Divide each dimension by the side length of the cube
3 and 2/3 => 11/3
1 and 2/3 => 5/3
2 and 1/3 => 7/3
(11/3) / (1/3) = 11
(5/3) / (1/3) = 5
(7/3) / (1/3) = 7
Now, multiply each of those values together
11 * 5 * 7 =>
55 * 7 =>
385
385 cubes with 1/3 inch sides can fit