I fear a virus was installed in my phone

Averge, this pop up has hit me many times, and you just have to ignore it. You said that you downloaded it, so the first step would be to run an antivirus scan. McAfee is a good program for this. You can find it at https://apps.apple.com/us/app/mobile-security-privacy-app/id724596345. Run a scan using the app, I promise this is legit. I have used this myself and it is very useful. After you run the scan, whether it finds anything or not, is to change your Apple ID password and watch your credit card for suspicious activity (If your credit card info is on your iPhone). I would also change any passwords that you have saved to your phone, like Emails. Hope this helps!

It is unnecessary and useless to run an antivirus scan on an iPhone. And there is no antivirus product for iPhones that do anything useful other than transfer money from you to the company you bought it from. If your phone is not jailbroken an antivirus scan will never find anything.

iOS / iPadOS devices cannot be hacked or infected with Virus / Malware / Spyware by merely clicking on a link in Safari, unless you have intentionally downloaded spurious softwares or unauthorised apps directly from internet and installed on your device or/and have Jail Broken.

Add-on anti-malware and add-on anti-virus on Macs tends to be problematic. And the run-time environments and locked-down access for anti-malware on macOS are heading toward those of iOS and iPadOS, as iOS and iPadOS block most of the access that anti-malware employs, as that access is what malware tries to use.

The iPhone cannot be infected with a virus unless it has been jailbroken. You didn't get 3 viruses, you simply got a popup to try and get information from you. If you receive these again, it is a java script from the website you were at. Go to Settings>Safari>Clear History and Website data. Then power off the phone and back on again, then go about your surfing. Downloading the app was not a hack, and installing an app from the App Store cannot hack or install a virus on your iPhone either. Installing and scanning your iPhone with an anti-virus is not necessary, and it cannot successfully scan your device anyway due to the sandboxing feature of iOS. You will be just fine from deleting the app and clearing your web history.

I feel like a *****. Sorry everyone

Don’t feel bad; McAfee has to make money somehow. And the rest of your advice is spot on.

The only reason I recommended that one was because I know it’s not a scam

That’s reasonable. It is not a scam; hopefully, none of the apps in the app store are outright scams. And McAfee does some useful things, but finding viruses is not one of them.

Yeah, the only reason I know it’s not a scam is because I have it on my laptop.

You're welcome.