If you are not familiar with collections, check out my article on Getting Started with Collections.

The ansible-galaxy collection list command can be used to list the collection you have installed.

~]$ ansible-galaxy collection list

# /home/john.doe/.ansible/collections/ansible_collections
Collection        Version
----------------- -------
amazon.aws        6.1.0
community.docker  1.9.0
community.general 4.0.2

# /usr/share/ansible/collections/ansible_collections
Collection               Version
------------------------ -------
redhat.rhel_system_roles 1.0.1

Optionally, you can include the path to a specific directory that contains collections you have installed.

~]$ ansible-galaxy collection list --collections-path /path/to/collections
Collection        Version
----------------- -------
amazon.aws        6.1.0
community.docker  1.9.0
community.general 4.0.2