I think he means, what is the equivalent liquid volume for a given volume of snow?
It varies, of course, since snow comes in all types of flake geometries, is compressible, can absorb liquid water, and changes with time and temperature.
Density = mass/volume. Scoop out a sample of snow of known size, say one liter [about a quart]) and weigh it. Let's say you've got 80 grams of snow. Well, 80 grams of liquid water (at standard temp and pressure, though it hardly matters) would occupy 80 ml [small enough to fit in an approved container for carrying liquids into the cabin of an airplane in the US].
Since volume = width x length x height, you can calculate the equivalent depth of liquid water for any given area, if you know the density of the snow. A ballpark water-equivalent value for fresh, "dry" snow would be about 10% of the snow depth, but in some places snow can be much much drier than that. In an extreme case, a hundred cm of snow could melt down to half a cm of water.