Non-consumable in-app purchases will not be charged again.
Using the same iTunes Store account (ID) you originally used to purchase the content, attempt to purchase the content again. After entering your password, you should receive a prompt telling you that you have already purchased the content and asking if you would like to download it again. Click ‘Yes’ and the content should be downloaded to your device.
Of course you must be using the same iTunes Store account (ID) to get it.