Unless you want to modify the templates, you should not be opening them. Rather, you should be using File>New and then selecting the template as the basis of the document that you want to create.
The templates should be saved into the user templates folder for which the normal location is
C:\Users[User Name]\AppData\Roaming\Microsoft\Templates
If you do not see the AppData folder, in the File Explorer, click on Options on the View tab of the ribbon and then on the View tab in the dialog that appears and select the item "Show hidden files, folders, and drives". While there, it is a good idea to uncheck
the box for "Hide extensions for known file types".