If you need to change the URL structure of your site, but the content of the site is to remain unchanged (or change insignificantly), we recommend setting up a server redirect f from the old webpages to the updated ones. This way the Yandex robot will automatically index the new pages and remove the old ones from the search index. New webpages will also appear in Yandex search results as the robot indexes your site.
If both the content and structure of your site have changed, you must configure your server to return an HTTP 404 error message when the outdated pages are visited. The indexing robot will track these changes, and these pages will gradually be removed from the search results. You can also block such pages from being indexed in robots.txt to remove these pages from the search results more quickly. You can also read tips on how to make new webpages appear in the search results faster by following this link.