I have 1 droplet with 5 working sites in it. Trying to update the theme for one of them.

I'm trying to upload a theme in .zip format but get the error message "413 Request Entity Too Large" (via traditional Wordpress theme back end)

I am also connecting to my droplet using Filezilla, I'm trying to navigate to main directory.

It seems like /var/www/html is supposed to be the main directory, but I there is nothing there, only an index.html and an info.php.

If I got to /root/restore/httpdocs I see all of the sites in my droplet on it. I uploaded a theme to that location using FTP, but it doesn't show on WP backend. So my question is, what is the right directory?