In order to write the given number in standard form, you take into account that the factor 10^(-4) can be written as follow:
[tex]10^{-4}=\frac{1}{10^4}[/tex]Next, you consider that the number of the exponent in a 10 factor means the number of zeros right side number 1:
[tex]\frac{1}{10^4}=\frac{1}{10000}[/tex]that is, there are four zeros right side of number 1.
Finally, you write the complete number:
[tex]3.6\times10^{-4}=\frac{3.6}{10^4}=\frac{3.6}{10000}[/tex]