Hi ​@masanori kawaguchi, 

Welcome to Box Community, and we’d love to assist! 

Essentially, your files wasn't deleted instead what you have experienced is part of your Box upgrade. Since your account type has transitioned your contents will be inaccessible and it may take up to 24-hours. If it has taken longer than the expected ETA, please let us know.

Thanks for posting, and we look forward to your reply! 

Hello.  I upgraded from personal plan to Enterprise and all of my files and folders have disappeared.  It's been 24 hours

Hi ​@laeic, 

Welcome to Box Community, and I moved your post to this related topic, please join our discussion!

After your upgrade, your files may be inaccessible during transition.  Are your files still missing at this time? 

We look forward to your reply,