As I said above, if a site isn't working as it is, running an upgrade is not going to fix it. You need to work out what is wrong with the existing site and fix it first or you will never get it working and just create more problems upgrading an already broken site.

Have you looked at the backup of the database. Are the posts actually still present in the database tables? If not then they are gone and you won't be able to ever get them back unless you have an older database backup with them still intact.