I want to understand how to backup a single site from a multisite and install in another location

Hey. Let's say I have site X on mymultisite.com

I want to backup EVERYTHING, essentially a perfect image of site X, including UPLOADS and all media content, as well as plug-ins and theme, into another Wordpress installation.

So, from mymultisite.com --> anewsite.com or anewmultisite.com

Total. TOTAL backup. Everything. Images, content, plug-ins, themes. Everything.

If the entirety cannot be backed up due to themes & plug-ins needing to be installed previously on mynewmultisite.com or anewsite.com; then let's assume I have already installed the theme & plug-ins into the new location and now wish to copy * everything * including uploads, to the new site.

How is this done?

If not on the high-level, then how is it done through FTP?

A related question is, where are the specific uploads folders and data for specific sites in my multisite stored in the file directory in FTP/SFTP?