pH is the negative logarithm of concentration of H+. But there is a relationship between pH and pOH.
pH + pOH = 14
pOH = 14 - pH = 14 - 6.47 = 7.53
Similarly, pOH is the negative logarithm of the concentration of OH-
pOH = -log(OH-)
7.53 = -log(OH-)
OH- = 2.95 x 10^-6