Windows Security (Windows Defender Security Center in previous versions of Windows) enables you to scan specific files and folders to make sure they're safe. You'll be notified immediately if any threats are found.
To scan specific files or folders, right-click the ones you want then select Scan with Microsoft Defender. When the scan is complete, you'll see the Scan options page letting you know the results of the scan.
To turn on Microsoft Defender Antivirus in Windows Security, go to Start > Settings > Update & Security > Windows Security > Virus & threat protection. Then, select Manage settings (or Virus & threat protection settings in early versions of Windows 10} and switch Real-time protection to On. Microsoft Defender Antivirus will then automatically turn on. If you're running Windows 10 for Enterprise, turn on Microsoft Defender Antivirus by uninstalling all of your other antivirus programs.