Question 905354
1 liter = 1 cubic decimeter = 1{{{dm^3}}}
2.1 m = 21 decimeters = 21 dm
600 mm = 6 decimeters = 6 dm

What is the shape of the container?

If it a cylindrical tank with a 2.1 meter (21 dm) diameter and a 600 mm (6 dm) height,
its radius is  {{{21dm/2=10.5 dm}}} .
Then, since the volume of a cylinder can be calculated as
{{{Volume=pi*radius^2*height=pi*radius*radius*height}}} , the volume (in cubic decimeters, or liters)
that such a tank can hold (filled all the way to the rim) is
{{{pi*10.5*10.5*6=about3.14*10.5*10.5*6=about2077.11=about2080}}}
For practical purposes, you could easily fit 2,000 liters of water.