I want to duplicate the data in my excel file, What formula should i use that could automatically duplicate the data from one area to another?

=(cell) and then Enter in the cell where you want to make a copy of that data.

point your cursor on the data you want to copy, then hold your mouse then  right click and point your cursor to the space you want to copy

You can also try 

= (Empty cell )

-->click on the cell you want to duplicate and press enter. 

=<cell>

for example in colum you want to duplicate all of data of columns A, the formula is =A1:A(the last cell)