To simplify the expression \( 3^8 \cdot 3^3 \) using the Product Rule of Exponents, you can add the exponents since the bases are the same. The Product Rule states:
\[ a^m \cdot a^n = a^{m+n} \]
Applying this rule to the given expression:
\[ 3^8 \cdot 3^3 = 3^{8+3} = 3^{11} \]
So, the simplified expression is \( 3^{11} \).