Concentration of NaOH=Concentration of OH- ions (NaOH is a strong base)
Kw=1x10^-14 (at room temperature/25 degrees)
using Kw=[H+][OH-]
We can figure out the [H+]
[H+]=Kw/[OH-]
[H+]=(1x10^-14) / (0.300)
Now we can put our concentration of H+ value into -log[H+] to find the pH using the fact pH=-log[H+]
pH=13.48