Hi Sattar,
Drag and drop would be pretty handy, but wouldn’t change the order on your live site. You can solve both problems by continuing to fill in your Order Number field for each CMS item. After that, you can select your collection list in the elements panel and change the Sort Order to Order Number, Smallest to Largest (or whatever your preference is).
In the backend, you can also sort by one of your CMS item’s attributes by clicking this little icon all the way on the right-hand side 
and selecting the column you want to sort by, then clicking the column header (just like in a normal spreadsheet).