Just find the volume with the dimensions given. 10x25x2 = 500m^3
Once you find that, turn that into cm^3 because it'll be easier.
1m^3 = 1000,000cm^3
500m^3 = 125,000,000cm^3
Since cm^3 can be ml, convert that into litres
1000ml = 1L
125,000,000 = 125,000L