Rules for Significant Figures:

1. Leading Zeros: Zeros to the left of the first non-zero digit are not significant. ($0.00$ are not significant).
2. Non-zero digits: Are always significant ($3$ and $4$ are significant).
3. Trailing Zeros: Zeros to the right of the decimal point and after a non-zero digit are significant ($0$ at the end is significant).

• Conclusion: The digits $3,4,$ and the trailing $0$ are significant. Total = 3.