Editing An Absolute Beginner's Guide for the RP2 (section)

=== Before turning on your RP2 ===
If you would like to use a larger micro SD card of your own, rather than the 32GB card that came with your RP2, follow these steps:
# Using a micro SD card reader, connect the included 32GB micro SD card to your computer. If you are told that the card is damaged and must be repaired or formatted, DO NOT DO SO. Your included card is almost certainly fine. Try using another card reader or computer if you cannot access your card at all.
# Copy ALL the files and directories from the included card to a safe place on your computer. I know that they look like random garbage, but they're actually just encrypted, and can only be opened with RetroidOS.
# Safely eject your included micro SD card.
# Connect your new micro SD card to your computer.
# Format your new micro SD card as "exFAT" format. The exact steps for doing this vary from computer to computer, so you may need to look up how to do this separately, as covering every possibility is outside the scope of this guide.
# Copy all the files and directories that were originally on your included micro SD card from your computer to your new micro SD card.
You should now be able to use your new micro SD card in place of the included micro SD card.