The property of negative integer exponents states that \( a^{-n} = \frac{1}{a^n} \).
Applying this to \( 3^{-4} \):
\[ 3^{-4} = \frac{1}{3^4} \]
Now, we need to calculate \( 3^4 \):
\[ 3^4 = 3 \times 3 \times 3 \times 3 = 81 \]
Thus,
\[ 3^{-4} = \frac{1}{3^4} = \frac{1}{81} \]
So, the final answer is:
\[ \frac{1}{81} \]