MS made management of Windows Store Apps really hard. If something is even possible, it’s only possible with some ugly PowerShell command.
If you somehow deleted the Windows Store App there is no easy way to re-add it.
PowerShell command to get your Windows Store back (adjust path to your environment):
Add-AppxPackage -DisableDevelopmentMode -Register "C:\Program Files\WindowsApps\Microsoft.WindowsStore_2015.8.3.0_x64__8wekyb3d8bbwe\AppxManifest.xml"
There is the Windows Store again…
Browsing C:\Program Files\WindowsApps is totally blocked. Don’t ask me why because if you do know the subfolder name, it is accessible. Run the command as admin and you’re fine.