Okay, I'll add what tells me that the update request page is missing.
Here is a record of changes of MongoDB and everything that the new version provides: https://docs.mongodb.com/manual/release-notes/4.2/
On the download page are all the components that can be downloaded, including the tarball file: https://www.mongodb.com/download-center/community
But just in case here is the source's tar file: https://fastdl.mongodb.org/src/mongodb-src-r4.2.3.tar.gz
What version to which version to update?
Currently the repository has version 4.0.12 to version 4.2.3 which is currently the last available version.