what volume of 0.4M sodium chloride will contain 0.585g of NaCl

Answer 1

molar mass NaaCl = 58.5
mols NaCl in 0.585 g is g/molar mass = 0.585/58.5 = 0.01
Then M = mols/L. YOu know mols and you know M, solve for L.
Convert to mL if required.