You'll probably have already run the sfc /scannow command in an elevated command prompt. Chances are, it found corrupt files and was unable to correct them.
You, therefore, moved onto executing dism /online /cleanup-image /restorehealth which then presented you with the following error message.
How to fix 0x800f081f when running DISM
From an elevated command prompt, enter dism /online /cleanup-image /startcomponentcleanup
Once this completes, run sfc /scannow and finally, re-run the original dism /online /cleanup-image /restorehealth command and you should be good.
Alternatively, download the Windows 10 ISO tool to upgrade your computer to the latest version. This should also correct the corrupt files.
We personally run this after running all the above commands.