The Uconnect system works well with these:
USB types are either FAT16, FAT32 or NTFS
For the file types: (*.wav), (*.mp3), (*.wma), (*.aac), (*.m4a or m4b) file extensions
And yes, USB size does matter, it all comes down on what you’re using it for. You can go with 32GB or 128GB USB sticks.