There is no software that can do a virus scan on your iPhone. Each application is sandboxed and cannot scan other files on it. Visiting a risky website will not install a virus on your iPhone as applications cannot be installed over the web. System files are locked on a read only partition that will not allow any changes.
To resolve your issue, it would be best to provide screenshots to be able to determine the cause. When visiting sites in the grey area of the internet, you will always see popups that are intended to scare you by claiming you have a problem and it can be resolved either by calling a fake support number or by paying for a service that claims to protect you. Any popup you see when using the internet are provided by the website you are visiting and those sites are paid to display that popup. It appears some of these sites have had the desired effect by making you believe that you have a virus. Don't fall for it.