Migrating BizTalk 2006 R2 sources to BizTalk 2013 R2

Problem:
You cannot directly migrate BizTalk 2006 R2 sources to BizTalk 2013 R2.

Solution:
You need to convert your BizTalk 2006 R2 sources to BizTalk 2010 and finally convert from BizTalk 2010 to BizTalk 2013 R2