How can I test my Windows 10 PC for a virus?

In case you have Windows 10, you may open Windows Defender and run a full system scan with it.

You may try Windows Defender Offline too, take a look at https://support.microsoft.com/en-us/windows/help-protect-my-pc-with-microsoft-defender-offline-9306d528-64bf-4668-5b80-ff533f183d6c