Hi,
first upgrade to 11.o.6000. this will be RU6
after that you need to apply RU6a ( 6a is only a patch which can be installed on RU6)
Migrating to Symantec Endpoint Protection 11.0 RU6
from 2000 you can migrated to 11.0.6000
http://www.symantec.com/business/support/index?page=content&id=TECH131653&locale=en_US