final cut file will not share

I have a long movie in Final Cut pro. I'd like to post it on Youtube. I've done this dozens of times before but now the file won't share. This is probably because the external drive I'm using is formated in ExFat, whatever that is. I don't have space on my main computer to share the file. I'd reformat the external drive, but my camera video files are already on that drive and they'd be lost.

Do I have to buy another external drive? Is there a way to share to Icloud? Can I share directly to Youtube?

Any ideas helpful.