Understanding the Problem
To find the total number of 3-digit numbers using natural numbers with non-repeating digits, we need to consider the range of digits available and the structure of a 3-digit number.

Available Digits
- Natural numbers include digits from 1 to 9.
- This gives us a total of 9 digits to choose from.

Structure of a 3-Digit Number
A 3-digit number can be represented as:
- Hundreds place
- Tens place
- Units place

Choosing the Digits
1. **Hundreds Place**:
- We can choose any digit from 1 to 9.
- This gives us **9 options**.
2. **Tens Place**:
- Once a digit is chosen for the hundreds place, we cannot use it again.
- Therefore, we have **8 options** left (one less than the total).
3. **Units Place**:
- After choosing the digits for the hundreds and tens places, we have 2 digits already used.
- This leaves us with **7 options** for the units place.

Calculating the Total
To find the total number of unique 3-digit combinations, we multiply the number of choices for each place:
- Total = Number of choices for Hundreds × Number of choices for Tens × Number of choices for Units

Mathematical Expression
- Total = 9 × 8 × 7

Final Calculation
- Total = 504

Conclusion
Thus, the total number of 3-digit numbers that can be formed using natural numbers with non-repeating digits is **504**.