This is the main path to stored Html file only /public_html/wp-content/themes/here your theme name/
and post and pages are stored in a database table name wp_posts
If you more details about it go and check Where are WordPress Pages and Posts Stored
It depends how you want to uniquely identify users. Some options to uniquely identify people might be the:
The Wordpress User ID. If people are logged in then using their WP User ID is a good option.
The Wordpress session ID. This is unique to the session; People will get a new session after some amount of time, and if they change browser or clear their ...
I don't know how the migration was executed, but here are some things that have caught me out in the past.
Files: Check the .htaccess and wp-config.php files.
htaccess for a multisite should look something like this:
RewriteRule ^index\.php$ - [L]
# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $...