How SP generates ID for each list item

When you create an item in a list, SharePoint assigns it a unique ID that it keeps for its entire life. This ID is what you are seeing in the URL for DispForm.aspx. If you need to be able to create URLs that link directly to a specific item, you will need to query the SharePoint list to get the ID, and then generate the URL yourself.

Two easy ways to query a SharePoint list's items programmatically are using the REST API or Web Services, namely Lists.GetListItems.

If you do not need it to be 100% programmatic, you might simply create a view that shows the list item's ID, export your list items to Excel, and then build links using Excel's HYPERLINK function.