You need to know the density of the liquid propane which does vary significantly with temperature. Once you know the density, you know how much mass your 3200 litres represents. At typical value for the density of propane at 60F is about 32 lb/ft3.
The gas volume is similar. You know the mass of gas, you need to calculate or lookup the density which is a factor of pressure and temperature. Density of propane density is available from the ASHRAE data books, Perry's Handbook of chemical engineers or you can calculate it.
For a gas, density = P*MW/(Z*R*T).
Density is lb/ft3
P is pressure, psia
MW is molecular weight, 44 for propane
Z is the compressibility factor, it depends on the pressure and temperature. For 100 or 200 psig and ambient temperatures, you can take it as 1.0.
R is the gas constant, 10.73 psia*ft3/lbmole/R
T is the temperature is degrees rankine.