See similar Taskbar programs as different icons

If you open multiple instances of the same program, such as a number of Word documents, you’ll see a stacked group of Word icons on your Taskbar. To open a specific document, you need to move your cursor over this stacked preview, to reveal all of them, then click the one you want. If you want to see each document as a separate Taskbar icon, then right-click any blank area on the Taskbar and click Properties.

Now click the ‘Taskbar buttons’ dropdown menu and change it from ‘Always combine, hide labels’ (which is the default setting) to ‘Never combine’. Click Apply, then OK.