When I obtain a number from an Excel database to insert it in a Word document, how can I edit that number on Word??

Define edit? You can't change the data you are pulling from Excel unless you do the merge to another document.

When word import the number from the excel database the number is displayed with 10 decimals and I want to edit the number to change it to just 2 decimals. How can I do that?

The primer on this page shows how to set the decimal value "rounding" values in your Mail Merge field switches.

Changing How Word Displays Numbers in Mail Merge

Thanks for your support. Great answer.