You need to move all backup jobs and their chains from an old repo (DD CIFS) to a new repo, which is DD Boost, correct?
Correct, but the old repo using DD CIFS is on one physical DD unit, and the new repo using DD Boost, is on a totally different unit.
You can use File Copy Job for that.
And how are you thinking you can use a File Copy job for this when the DD CIFS repo isn't mapped to the Veeam server, and the target DD Boost repo cannot be mapped through the OS? File Copy jobs will copy locally-accessible files on the source to a destination that must also be local (to that destination).
The article you provided, while useful, assumes that the physical source and destination are on the same DataDomain unit, and this is not my case.