Here's how to get there:

1. Move the decimal point to the right until you have a number between 1 and 10. In this case, we move it five places to the right, giving us 8.1.

2. Count the number of places you moved the decimal point. Since we moved it five places to the right, the exponent is -5.

3. Combine the number and the exponent to get 8.1 x 10^-5.