I want to save the position of list items after drag and drop. So that when next time I will open the same page then I will get the previously changed position of list items.
Create a Table in your database for that, and save the position of the items in there. Like this you can access the position-data easily.
The following link could prove to be useful to you. It involves drag and drop seating arrangement but at least you could get a start after going through the link.