You are mixing your units. Meters are length and gallons are volume. But if you meant "liter" instead of meter, then it makes sense. There are 94,635.3 liters in 25,000 gallons (for a US liquid gallon).
There are 3,170.0646 US gallons of water in 12 cubic meters.
If you have 208,000 cubic meters of water you have: 54,950,000 US gallons OR 45,750,000 UK gallons.
1.35 cubic meters is 356.632 gallons.
300,000 Imperial Gallons = 1,363.827 Cubic Meters
Eight cubic meters of water equates to 1,759.75 Imperial gallons.
3,267.279944 gallons.
132.086026 gallons.
240,466.6 US gallons.
338.25
54 US gallons of water equates to 0.204412 cubicmeters.
10,000 US gallons of water equates to 37.854118 m3
79.25 gallons are in 0.3 cubic meters.