To tell Google that a page has moved, you can use a 301 redirect. A 301 redirect is a permanent redirect from one URL to another and signals to search engines that the page has moved permanently. To implement a 301 redirect, you can add a line of code to your website's .htaccess file. Here is an example of a 301 redirect in Apache:
Redirect 301 /old-page.html http://www.example.com/new-page.html
Additionally, you can use the Search Console's Change of Address tool to inform Google of the move. This tool is helpful when moving your entire website to a new domain.
It is important to note that it may take some time for Google to reflect the changes and update its index accordingly.