Client/Server Application by which User can upload folder using file loader

Anvil may not have a custom-fit solution for you, but it does give you the tools to build this kind of functionality, if you first take the time to understand how they work and how they can be linked together using everyday Python features. This may be a good starting point:

As for

I see an information problem: each PC contains thousands of folders. If the client does not specify a folder name, then how will your Anvil code know which of these to upload from?