Since the molar mass of KOH is 56.105 g, you have 250/56.105 = 4.456 moles of KOH in 2.585 litres of solution, so the molarity is 4.456/2.585 = 1.724 M.
If you calculate the number of moles in 2500 mL of water and assume that the density of the solvent, water, is 1 kg/litre you obtain the molality m = 1.782 mol/kg
