Hello Felipe,
well if you do need to format it absolutly.
Make sure to do a backup of the license folder!
Then format it in ext4 and copy the License folder back onto the SD.
Also make sure that you do not change permissions etc. of those files!
Still it is recommended that you do NOT format it but instead just delete everything but NOT the License folder...
To read the SD card you will need a linux OS or a plugin for windows that enables ext4-filesystem support
kind regards,
Oliver
Phoenix Contact Electronics Headquarter - PLCnext Runtime Product Management and Support