You can check the Charm Pack Center inside the Charms Arena, next to the trading button located at the bottom of your screen. Here you will find all your collected packs.

Tap to open your Charm Packs

Each Magical Pack will offer an option to re-open the pack. Use the "Reopen” button to reshuffle the Charms inside your pack. Choose it wisely because there is always a chance to get the same charms or to get new charms - good luck!