Migration path
For a general overview on the migration visit What is Confluence Cloud Migration Assistant?.
The migration is fully automatic using Atlassian’s App migration platform.
Manual steps after migration
There are currently no further steps required.
Migrated data
All app data will only be migrated, if they do not exist in the Jira Cloud instance.
Existing app data in the Jira Cloud instance will not be overwritten.
Personal calendar settings
Space calendar settings
Page calendar settings
Feature differences Cloud vs. Server for Outlook Calendars for Confluence
Basically you will have the same features on Cloud as on Server. You will get additionally the option to show Jira issues from a filter, using any date field and to share Jira data with users without a Jira account.