I think it's possible if i buy both instances in the same operation, but i'm not sure if it's possible buying them separately.
You can add Confluence to your current JIRA Cloud instance at any time from the "Discover new Applications" section and it will be added in that url /wiki
For more info https://www.atlassian.com/licensing/cloud/managing
Atlassian Summit is an excellent opportunity for in-person support, training, and networking.Learn more
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG