Regardless of the SharePoint upgrade method chosen, you simply run the Nintex Workflow 2010 installer on the SharePoint 2010 server.
If you are doing an “in place upgrade” on SharePoint, uninstall Nintex Workflow 2007, and then run the Nintex Workflow 2010 installer after the SharePoint upgrade is complete.
If you are doing a content database migration, move the Nintex configuration database to the SharePoint 2010 server and then run the Nintex Workflow 2010 installation and point to the existing Nintex configuration database.
If you are moving the database to a different server or database name, please pay special information to Stage 2 - Update the references to the content databases of the ‘How to move a Nintex Workflow 2007 database’ document (http://connect.nintex.com/files/folders/tutorials/entry1213.aspx) to update internal references to the old server name stored within the database.