How do I convert 3,959.79 meter cubic to kilogram

edit: i was wrong! dont listen to what i said

You can't convert from volume to weight without having a density.

A cubic meter of feathers weighs a lot less than a cubic meter of neutronium.

You don't mention a density.  Do you have one?

(for the pedantic:  technically density gets you from volume to mass, and then you have to apply

the gravitational acceleration of whatever planet you happen to be on to get the weight.  As most

of us spend 100% of our time on Earth it's fairly common to see densities expressed as a

weight per unit volume, just including Earth's gravitational acceleration in the constant.)