Windows Update logs are now generated using ETW (Event Tracing for Windows).
Please run the Get-WindowsUpdateLog PowerShell command to convert ETW traces into a readable WindowsUpdate.log.
For more information, please visit https://go.microsoft.com/fwlink/?LinkId=518345
https://docs.microsoft.com/ja-jp/windows/deployment/update/windows-update-logs
Windows Update のログ ファイル