If you use the same Google Account, you can use the Premium Plan on your other Android devices once you have subscribed.
On the device that doesn't have the Premium Plan yet, open the settings screen, tap "Premium Service", and tap "Restore Subscription" to apply it.
If that doesn't work, make sure the Google Play Store app is signed in with the same Google Account you used for the purchase, restart the device, and try again.
※ A Premium Plan purchased on the iPhone/iPad version (through the App Store) cannot be carried over to the Android version. See "Can I use a Premium subscription bought on iPhone on the Android version?" for details.