Performing a security scan on my Apple device

The closest you'll get is Safety Check, which is a feature which allows you to quickly view and reset who and what they have access to on your iPhone, such as location services. You can do that in Settings > Privacy and Security > Safety Check.

But if you want to scan for malware and viruses, that isn't possible to be installed or run.

It's a user to user forum. We can't scan your iPhone, and neither can Apple for that matter. What security issue are you concerned about.

Nothing has access to your file system to scan anything. Luckily that is also why there cannot be viruses installed in the file system either, so any such scan is meaningless.

If you are having an issue, describe what that is and feel free to post screenshots to help visualize what you are seeing as long as they do not include any personal information.