How can I download all the uploads at once?

I have to check  all the uploads of 315 forms and I want to do it very fast

You can download your submissions' file uploads by following this guide: https://www.jotform.com/help/356-How-to-Download-the-Submission-Files 

Or you can export your data all at once by following this guide: https://www.jotform.com/help/374-How-to-export-all-of-your-data-at-once 

Let us know if that helps.