The upgrade process continues with Microsoft Dynamics GP 2013 Upgrade Paths – GP, Windows, SQL Server-
Microsoft Dynamics GP 2013 Upgrade Paths – GP, Windows, SQL Server – Dynamics GP Support and Services Blog – Microsoft Dynamics GP – Microsoft Dynamics Community
Install, Upgrade & AdminMicrosoft & the GP EcosystemGP 2013
Archived post from 2013. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.