Easiest way is to enable sync service (a Pro feature) on your old device and make sure that all your designs are synced to cloud. Use same Facebook or Google account to login on new device and your designs will be restored. Alternatively you can go to your room, click "Export" icon and choose "Export link" option. Save that link somewhere (you can send e-mail to yourself). On new device install the app and click on saved link. That will restore your design.