As I understand, you want to write a diameter, that currently is in scientific notation, in standard notation.
The standard notation is 0.0000084
First, scientific notation is a way to write really long numbers (particularly those that have a lot of zeros) in a shorter way.
The general form is:
Ax10^n
If n is positive, we add n zeros at the right of our number.
If n is negative, we add n zeros to the left.
Here we have:
8.4x10^-6
So n is negative, meaning that we need to add the zeros at the left (also remember to correctly change the position of the decimal point) we will get:
8.4x10^-6 = 0.0000084
This is the measure in standard notation.
If you want to learn more, you can read:
https://brainly.com/question/1705769