SketchClub provides many different ways for transferring and making backup copies of your sketches. Your sketches are automatically included in your nightly iCloud backup so getting a new device brings your data over simply.
With a sketch open on your canvas, open the Actions Panel and tap the "Export / Share" icon. Choose the .sketchClub format and then you can choose to send the file to another device with AirDrop or to save the file to your iCloud, DropBox, or other cloud storage for access from other devices.
In your Local Gallery tap the Select button in the toolbar at the top of the screen. You can then tap to select each sketch you want to transfer or tap the Select All button. Then tap the Share button in the bottom toolbar, choose the .sketchClub format, and then you can choose to send the files to another device with AirDrop or to save them to your iCloud, DropBox, or other cloud storage.