Step 1: Analyzing the derivative.
Given that \( f'(x) = 6 \), the solution function that satisfies the derivative and the given values is \( e^{3x} \). The function \( f(x) = e^{3x} \) satisfies \( f(1) = 3 \) and \( f'(1) = 6 \).
Step 2: Conclusion.
The correct function is \( e^{3x} \), corresponding to option (3).