For most purposes, a UNC path is just a local path. So upload from a UNC path to SFTP, is not much different to any other upload.
Start here:
Automate file transfers (or synchronization) to FTP server or SFTP server
WinSCP GUI can generate an upload script for you:
https://winscp.net/eng/docs/guide_automation#generating

Hello,

I am asked to prepare a bat file for file copy from UNC path to the SFTP location.
Since I am not familiar with this environment I struggle to even begin. I was looking for some useful info, but everything is either too advanced and therefore enigmatic to me or not regarding UNC to SFTP movement.
I saw some basic copying with xcopy usage, but it does not explain how do I setup connections in the script etc. Since GUI does not allow me to connect with UNC path, I don't know how to properly write it.
Could someone please share some example script I could adapt?