Precalculus: Converting Fractions to Exponential form; Solution of the set.?

So here's an example of the entire question with the answer.

Solve:
3^x = 1/9 ...you write each side of the question as a power of 3

Like this, 3^x = 3^-2

so the solution of the set is -2

OKAY SO HERE's MY PROBLEM!
How in the hell do you convert the fraction (1/9) to an exponent (3^-2)
i don't know how to do that.

HELP!

You know that 9 = 3², so 1/9 = 1/3² = 3⁻²

I'm going to work this in reverse, if you don't mind.
3^-2
1/3^2 < a number raised to a negative exponent is just that number to that exponent (but positive) over 1.
1/3⋅3
1/9