Your subscriptions are automatically restored when you login to your mobile app account.

It is essential that you have the same App Store ID (Google Play ID for Android and iTunes account for iOS) on the new device for the older subscriptions to be carried over from the old device to the new. This is applicable, if you purchased the subscription through iOS/Android App Stores.

If you purchased your subscription through BigCommerce marketplace, your email account has the associated subscriptions irrespective of the device or mobile operating system.