The molarity of a solution is defined as the number of moles of solute per liter of solution. To calculate the molarity of the given solution, we need to first determine the number of moles of NaCl present in 300 grams.

The molar mass of NaCl is approximately 58.44 g/mol. Therefore, the number of moles of NaCl in 300 grams can be calculated as:

Moles of NaCl = Mass of NaCl / Molar mass of NaCl

Moles of NaCl = 300 g / 58.44 g/mol

Moles of NaCl = 5.134 mol

Next, we need to determine the volume of the solution in liters. The given volume is 3000 liters.

Finally, we can calculate the molarity of the solution by dividing the number of moles of NaCl by the volume of the solution in liters:

Molarity = Moles of NaCl / Volume of solution

Molarity = 5.134 mol / 3000 L

Molarity ≈ 0.001711 M

Therefore, the molarity of the given 3000 liters solution containing 300 grams NaCl is approximately 0.001711 M.