I got the your Mac is infected with virus scam and I clicked scan

no, the only means to install software of any kind that would include malware and scams is apples app store

you can't install stuff from links or browsers or mails or sms

if you accept stuff then you can have it add a scam calendar Delete spam calendars and events on iPhone - Apple Support

or if you go to s phishing site and provide them with your appleID and password then you could compromise your account

If you think your Apple ID has been compromised - Apple Support

&

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Scam.

See >>> Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Providing your iPad has been kept up-to-date with system software updates, you should not be overly concerned for your iPad being directly compromised. Provided you have not given away any personal or financially sensitive information, you or your data are unlikely to have been compromised. If you have inadvertently exposed any account credentials or credit card information, change passwords immediately - and inform the relevant card issuers or financial organisations.

Due to the system architecture of iOS/iPadOS, unless jailbroken, your iPad is not susceptible to traditional malware infection per-se. However, as with all computer systems, there are still vulnerabilities and exploits to which you remain vulnerable. For older devices, no longer benefiting from regular security updates, the risk of an unpatched vulnerability being exploited increases. Regardless of the installed version of iPadOS, there are useful mitigations that can be used to significantly reduce your expose to risk.

There are no AntiVirus scanning products for iOS/iPadOS. Due to the sandboxed security architecture, an AV process is unable to scan the filesystem.

Providing that you have not attempted to jailbreak your device - or have bypassed protections by side-loading third-Apps (if you don’t know what this is, then don’t worry about it), then it is highly unlikely that your device will have been infected with a virus or other malware.

Most alerts that you see are pop-up messages from websites - these being designed to scare the unwary into giving away sensitive information - or to fool you into doing something that you shouldn’t.

Browser-based attacks can largely be mitigated by installing a good, trusted, Content and Ad-blocking product. One of the very best and most respected within the Apple App Store - designed for iPad, iPhone and Mac - is 1Blocker for Safari.

https://apps.apple.com/gb/app/1blocker-for-safari/id1365531024

1Blocker is highly configurable - and crucially does not rely upon an external proxy-service of dubious provenance. All processing takes place on your device - and contrary to expectations, Safari will run faster and more efficiently. 

Unwanted content is not simply filtered after download (a technique used by basic/inferior products), but instead undesirable embedded content blocked form download. A further benefit on metered services, such as cellular connections where you data may be capped or chargeable, this not only improves speed but also saves you money.

When using a good quality Content blocker, a high proportion of otherwise inescapable risk when using your Safari browser, or linking to external sources from email, is effectively mitigated before it even reaches you.

There are additional protections that can enhance protection further, such as using one of the better Recursive DNS Services in preference to automatic settings. This can either be set on a per-device basis in Settings, or can be set-up on your home Router. I recommend using one of the following services, for which IPv4 ad IPv6 server address are included here:

Quad9 (recommended)

9.9.9.9

149.112.112.112

2620:fe::fe

2620:fe::9

OpenDNS

208.67.222.222

208.67.220.220

2620:0:ccc::2

2620:0:ccd::2

Cloudflare+APNIC

1.1.1.1

1.0.0.1

2606:4700:4700::1111

2606:4700:4700::1001

Use of the above DNS services will help to shield you from “known bad” websites and URLs - and when used alongside 1Blocker, provides defense in depth.

I hope this reassurance and guidance proves to be helpful in resolving any issues with malicious websites. If nothing else, an upgrade of the “human firewall”, through awareness and diligence, is one if the most important defences.