Safari-Alert Virus

I recently got the Safari Virus Alert thing on my iPad mini and because I was freaking out I decided to call the number, they asked me to provide the serial number of my iPad and then told me they would "fix" the problem, but as soon as they asked for my credit card information I hung up. After some time, I cleared all the web history and data on my iPad mini and saw the pop up was gone. I was just wondering if I should be worried about the serial number and what I can do to resolve that.

I would really appreciate your help, thank you very much.