Your purchased themes and content are all backed up to your SwiftKey Account. Just as apps you download from Google Play are assigned to a Google account, your SwiftKey Keyboard content works the same way.
When you download SwiftKey Keyboard on your new phone, be sure to sign into the same SwiftKey Account that you used to purchase your content from the SwiftKey Store.
If you need help creating/signing into a SwiftKey Account, see the instructions here.
Once you are signed in to your SwiftKey Account, you can access your previously purchased themes in the following way:
- Open the SwiftKey Hub
- Go to the themes panel
- You will see your previously downloaded themes in the carousel
- Tap 'SwiftKey Store' to see all your previously purchased themes (and new themes to purchase/download)
If you are unable to select your previously purchased themes in the SwiftKey Store, please see this article.