@katz515 - all right so the integer is the ID of the folder. It is not required that you include one, leaving it blank will just upload the file to the root of the file manager.
You can find the folder ID in the file manager GUI presently - when you’re in the dashboard, the ID of the folder is the last path of the URL.
There is not currently an endpoint to create (or other operations) folders but there is a Github issue coming in to outline that, and a few other endpoints that would be helpful.