Apologies, I spelled it out wrong here in this question. Here is a more detailed output which I copy pasted from the docs.
$ sudo yum install -y mongodb-org
Loaded plugins: extras_suggestions, langpacks, priorities,
: update-motd
amzn2-core | 3.7 kB 00:00
amzn2extra-docker | 3.0 kB 00:00
amzn2extra-kernel-5.10 | 3.0 kB 00:00
mongodb-org-5.0 | 2.5 kB 00:00
mongodb-org-5.0/primary_db | 77 kB 00:00
No package mongodb-org available.
Error: Nothing to do