Migrating Projects from Earlier Versions : Project Migration Overview

Project Migration Overview
Many of the actions you must take to migrate projects to the current release depend on the version you are migrating from, and the features you use.
Some manual steps are required. More manual steps are required for earlier versions than for 4.x projects due to the changes in architecture.
If you are upgrading from a version earlier than 3.0, first upgrade to the latest 3.x version, following directions in the 3.x documentation.
Check Release Notes
Check the new features, changed functionality, and the deprecated features lists in Release Notes and take action accordingly.