For a box that is an exact cube with a full-capacity water load equal to 3375 kilograms,
one would write the density (or mass per unit volume) of water, given by one
online source as 997 kilograms per cubic meter. Then divide:
3375 kg
--------------- .
997 kg/m3
This gives a quotient or box volume of 3.385155466 m3.
Then find the cube root of 3.385155466 m3 to gain the length (as well as width and height)
of the cube as 1.501503007 meters.