Unable to copy a DB from SQL Server 2000 to SQL Server 2012 using copy wizard
The supported upgrade path does not go directly from 2000 to 2012.  You will have to have an intermediate step where you upgrade or restore those DBs to a 2005 or 2008 R2 instance.  Once you've done that, you can upgrade to 2012 or take a backup of the DBs in 2005, then restore them on to 2012.

We are migrating to 2014 as my company is on 2005 SP3 right now.