How do you write 6,301.005 in standard form

One of ...

It depends on where you are.

In the US, standard form is the way you have written the number. Your number would be 6,301.005.

The attachment gives some guidance for number formats in American publications. In certain publications, thin spaces are used instead of commas to separate groups of digits. The comma (or space) is often optional, but can enhance readability for large numbers.

In Britain, standard form is the form called "scientific notation" in the US. Your number would be 6.301005×10³.