How do you write 3^2=9 in logarithmic form?

It is ##log_3 9=2##
By definition the logarithmic form ##log_b x=y## is equivalent to the exponential form ##b^y=x##
Hence from the given ##3^2=9## you have ##b=3## ##y=2## ##x=9##
hence the logarithmic form is ##log_3 9=2##