Mary,
To see the reports button, your workflow user record must be at least Process Administrator (use the admin module to see an individual person's properties, in the Privileges tab I think..)
The backend stores information suchs as where and when a workitem was processed, but it won't contain the information that was populated on the forms, unless you make the fields you need to searchable fields on the process map. Beware, this can add to the size of the database quickly.
All of the available tables are documented in the pdf files that are distributed with the product.
Good luck,
Sanna