I had something pop up saying I had a critical threat nine viruses in my phone is this real

1. Open the Calendar app.
2. At the bottom of the screen, tap Calendars.
3. Look for a calendar that you don't recognize. Tap the More Info button  next to that calendar, then scroll down and tap Delete Calendar.

If this doesn't fix the issue, delete the calendar subscription in Settings:

1. Open the Settings app.
2. Tap Calendar > Accounts. Or if you use iOS 13, tap Passwords & Accounts > Accounts instead.
3. Tap Subscribed Calendars.
4. Look for a calendar that you don't recognize. Tap it, then tap Delete Account.

Ignore it. That’s a phishing scam to get you to provide information so criminals can steal your money or your identity.

Click this Apple support link for more info→Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support