When using Safari on your iPadOS iPad - and downloading the “desktop” version of a webpage (this is the iPadOS default setting) - your browser reports to the website that it is a Mac. The website, malicious in this case, believing that you are something that you are not, is trying to convince you that you have virus - and wants you to click on something that you shouldn’t!
This is a classic “bait” attack - that wants to install something nasty on your device - or convince you to part with something you shouldn’t.
As the previous responder has indicated, this is a scam.
Some things that you might like to consider in avoiding (or a least, significantly reducing) exposure to attacks of this nature:
1) Manually change the DNS settings on your device to point to Quad9 DNS Servers (Primary 9.9.9.9, Secondary 149.112.112.112) - as this is “filtered” recursive DNS service that prevents resolution of known “bad” addresses/sites.
2) Install the 1Blocker-X App - this can block the majority of “bad” content.
Hope you find this helpful.