All good. You don't have to pay twice. Follow these steps:
1) Install the app on your new device
2) Click on Settings from the main menu (older apps may say "More")
3) Click "Restore Purchases"
4) Enter the same username and password for iTunes or Google Play you previously purchased content with on the other device.
NOTE: You may need to force close and reopen that app after.
If the above steps do not work, try purchasing the content pack again. If you use the same iTunes or Google Play username and password, you will NOT be charged twice. If you are still unable to restore content, we will be happy to refund you.