Assign a Dropdown list to a range of cells from values of other range

To best describe or illustrate your problem you would be better off attaching a dummy workbook.

The workbook should contain the same structure and some dummy data of the same type as the type you have in your real workbook - so, if a cell contains numbers & letters in this format abc-123 then that should be reflected in the dummy workbook.

If needed supply a before and after sheet in the workbook so the person helping you can see what you are trying to achieve.