You can open your mind maps on all your devices that have SimpleMind Pro installed. The easiest way is to sync your mind maps. To do so you can use built-in clouds or a cloud service.

Built-in Clouds

SimpleMind Pro uses built-in clouds to synchronize your mind maps across devices and all platforms. After connecting SimpleMind Pro to the cloud, that cloud tab will be visible in SimpleMind. You can open and save mind maps from within SimpleMind, all changes will be synched to that cloud.
The built-in clouds are:

Any cloud service (Not on Android)

SimpleMind for Windows, SimpleMind for Mac and SimpleMind for iPad/iPhone can store mind maps in any folder. Because of that you can store mind maps in a folder that is synchronised by a cloud service. For example, iCloudDrive or the Dropbox app. This cloud service synchronises your mind maps.
The AppStore edition is sandboxed. When you open a Mind Map this way, you cannot add or open links to external documents or mind maps.

Example of opening your mind maps on different devices (built in clouds)