To know the amount or volume of NaOH to prepare 400 mL of 1.5 M NaOH, we use formula

M1 X V1 = M2 X V2

V1 = M2 X V2/ M1

But before that we will convert 400 mL into litre = 0.4 L

5.5 X V1 = 1.5 M x 0.4 L

V1 = 1.5 M X 0.4L/ 5.5

V1= 0.10 L

V1 = 100mL

So, you need 100mL of 5.5 NaOH