Foreman 3.0 isn’t released yet. It is coming in the next while.
There are some docs available on our site because we ask the community to help us by testing our release candidates. For example: Foreman 3.0.0 RC2 is available for testing - the second release candidate is available at the moment and the more people who use it and tell us about their experience, the more stable the forthcoming release will be.
We will announce the release as soon as it is ready here, update our site, and on social media/demo etc. You can find all the latest release information and prep in our release announcement section: Release Announcements - TheForeman
You can keep track of the Foreman 3.0 release process here: Foreman 3.0.0(GA) release process