How many grams of naoh would you need to make 450 ml of a 0.250 m naoh solution

You have molarity and you have volume. Use the formula :
Molarity(M)= Moles(N)/Liter(L)            to get the solution. 
450 ml= .450 L
.250 = N/.450
N=.1125 moles of NaOH.
 And since you know the moles, use the molar mass to figure out the grams.
 (40g/mol NaOH) x (.1125 mol) =  
4.5g of NaOH.

Hope it helps. Good luck on chemistry.

High-energy and unstable.