Where is the information a form collects
If nothing, try Dashboard - Members - [username]. This would show custom attributes, which would look like a form when collected.
The actual data will be in the database. I gather you don't really want to know WHERE the data is, but rather how to find out WHAT it is.
Do you have full admin access to the concrete5 dashboard? It's possible that it you do not have complete access you're not seeing all the admin pages.