To apply the property of negative integer exponents, we can use the rule that states \( a^{-n} = \frac{1}{a^n} \).
Applying this rule to \( 3^{-4} \):
\[ 3^{-4} = \frac{1}{3^4} \]
Next, we need to calculate \( 3^4 \):
\[ 3^4 = 3 \times 3 \times 3 \times 3 = 81 \]
Now we can substitute this value back into our expression:
\[ 3^{-4} = \frac{1}{81} \]
Thus, the final answer is:
\[ 3^{-4} = \frac{1}{81} \]