Hi Janetm,
Sorry for not being able to reply to your query on time. As explained above, that all of your files are opening with the Adobe Reader DC which means that Reader DC has been set as an default application to open all the files of your computer.
You can simply change the the settings and set the supported application to open that particular file format.
There are two methods that you can fix this-
Method-1
- Right click on the file that isn't a .pdf and select Properties.
- In the file's Properties dialog box, click Change.

- Choose supported application, and then click OK.
Method-2
You can simply uninstall Adobe Reader DC and Reinstall. This time do not set the Reader DC as default to open all the files.
Hope this helps.
Regards,
Akanchha