Welcome to Android Central, where there are indeed iPhones, but not to the extent that there are at
https://m.imore.com/
If you are experiencing a scareware pop-up, you could try clearing your Safari browser cache.
If there is a website address on the pop-up, you may be able to add it as a blocked named site to your wifi firewall settings.
If you are using an app to scan your device for malware, let us know, but I'm guessing that you're not, and that these are just typical filth-lies-rubbish pop-ups.
A screenshot would help us to judge, so by all means post one.