Uploading all files in a folder in order

I have a process that will generate anywhere between 5 and 17 files nightly. These files will have to be uploaded in a certain order. Since I cannot predict which files will be generated nightly I have hard time figuring out how to write a script to upload files in correct order. In what order, by default, does WinSCP upload files? Does it use timestamps and go in ascending order?

What would happen if I have a command in the script to upload a file that doesn't exist? Will the whole process fail?

Thanks for the help!

WinSCP uploads the files in the order in which they are returned by Windows in the directory listing (so its in-deterministic).

By default the script fails when the file does not exist.
You can change this with option batch command:
https://winscp.net/eng/docs/scriptcommand_option