How to add a column into new datatablefrom existing datatable?

Hi,

Thank you for your support.
I would like to add a few question.

1.Can we add blank column?
I would like to make Datatable such as,

-New Datatable
Column1 | Column2 | Column3
Col3 data | | Col2 data
of existing DT| blank | of existing

  1. Can we use the column number insted of column name?

Best Regards,
Takuya