Confluence: Cloud と Server でのストレージ容量の比較
What are the storage capacities of Confluence Cloud vs Server?
サーバー版 / クラウド版
When it comes to storage limits have a look at Atlassian Cloud storage policy.
As far as Server limit, there is a default attachment size that applies to individual files uploaded (you can change this default). But for overall storage capacity, it depends on your hardware specifications and storage configurations.