How do you get the pH 13.68 into OH^-^?

pH + pOH = pKw = 14

pOH = 14-pH = 14-13.68 = 0.32
pOH = -log(OH^-)
0.32 = -log(OH^-)
-0.32 = log(OH^-)
(OH^-) = 0.479M