How to reindex a large site in PS?

Question

Search Engine Optimization

We moved the news site to a new engine (currently around 110k pages).
All links have changed, become readable, the structure has improved, but everywhere on the old links - 404 page.
How, in this case, is it right to inform search engines that a complete re-indexing is necessary?
Sitemap - I will generate and add it wherever possible, I will set up 404 redirects, what else can / should be done?

Answer 1

301 redirect - from old links to new ones - required. This will save positions in the search engine.
What is needed is complete - search engines will understand themselves by sitemap.xml
Create robots.txt and everything that does not need to be indexed - forbid and specify the sitemap file there.