Could you please help me to block this link or web ?

It is a SCAM. Don't even click the close button on that dialog, and do not click the Scan Now button. Do the following:

1. Force quit Safari (option+command+esc buttons, or control-click on the Safari icon on the Dock and select Force Quit there.
2. Press and hold the shift key while relaunching Safari.
3. Safari menu : Clear History… : all history : Clear History button.
   1. This will clear history and remove all cookies that have been set.
4. Safari Preferences : Advanced : [√] Show Develop menu on menu bar
   1. Press option+command+e keys to clear your browser cache
5. Safari menu : Quit

Download and run the free Malwarebytes for Mac to detect (if present) and remove any adware/malware that has been installed.

Do not visit the website that spawned the Virus page again.

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams.

Force Quit Safari.

Restart Safari while holding down the Shift key.

Don't go to whatever website you were visiting when that popped up.

If the popups return on clean websites, use MalwareBytes Anti-Malware for Mac to remove the Adware you installed.

Then read this so you don't try to install Adware in the future: How to install adware - Apple Community

EtreCheck is a simple little app to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac.

http://www.etresoft.com/etrecheck

Pastebin is a good place to paste the whole report...

https://pastebin.com/

Workable but harder for me to work with...the Note tool on the bottom of this editor's toolbar, as shown in the image, to copy and paste the output from EtreCheck.

That is either because the sites you visit have embedded javascript causing the popups, or you have installed adware that you didn't remove with MBAM.