In an Administrator CMD prompt, run
DISM /Online /Cleanup-Image /RestoreHealth
Detailed technical description of the DISM command from Microsoft
If this doesn't reinstall the Windows Store, you may need to install it from the .appxbundle file. First you can check whether it's already on your machine and can be installed by running the following in an Administrator Powershell session:
Get-AppxPackage -allusers Microsoft.WindowsStore | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
If that doesn't work, you'll need to get the .appxbundle file from Microsoft first. The easiest way to get the URL from Microsoft (and not an untrusted third party) is to go to https://store.rg-adguard.net/ and enter this URL which is the link for the Windows store https://www.microsoft.com/en-us/p/microsoft-store/9wzdncrfjbmp. Change the type from "RP" to "Retail" and it'll generate all the possible Microsoft URLs you may need. Assuming you don't need to reinstall .NET or the Microsoft VC libraries, you can just download the most recent Microsoft.WindowsStore*.appxbundle file. As of today, it's "Microsoft.WindowsStore_11811.1001.2713.0_neutral_~_8wekyb3d8bbwe.appxbundle"
Once you've downloaded that to your local machine, you may be able to double-click it to install it or run Add-AppxPackage -Path "Microsoft.WindowsStore*.appxbundle" from an Administrator Powershell in the same directory as you saved the .appxbundle.