Insert a helper column to the right of your current data column. In the
first cell of the new column, enter the following formula:
="0709-"&A1
Changing cell A1 to match the cell to the right of the formula. Copy the
formula down the column and then select all the cells in the column that
contain the formula. After selecting the column of formulas, click EDIT in
the menu and select COPY. Move to the first cell in your original column of
numbers, click EDIT in the menu and select PASTE SPECIAL. Click the VALUES
option button and click OK.
YOu can now delete the helper column