Sodium hydroxide (NaOH), being a strong base, fully dissociates in water. Consequently, the concentration of hydroxide ions (\( [\text{OH}^-] \)) matches that of NaOH, which is 0.001 M.
The pOH is calculated using the formula:
\[
\text{pOH} = -\log [\text{OH}^-]
\]
Substituting the hydroxide ion concentration:
\[
\text{pOH} = -\log (0.001) = 3
\]
Given that \( \text{pH} + \text{pOH} = 14 \):
\[
\text{pH} = 14 - 3 = 13
\]
Therefore, the pH of the NaOH solution is 13.