Question

calculate the weight of nacl present in 250 g of 0.01m solution

Answer 1

Your question says 0.01m which is 0.01 MOLAL. Since you apparently don't know how to use the caps key I suspect you mean 0.01 M (MOLAR) but I'll go with 0.01 m since you ask about 250 g solution.

0.01m means 0.01 mols/kg solvent. How many mols do you have in 250 g? That's 0.01 mols x (250/1000) = ? mols.
Then mols = g/molar mass. You know mols and molar mass, solve for grams.