You can’t do a bulk-update in SSIS within a dataflow task with the OOB components.
The general pattern is to identify your inserts, updates and deletes and push the updates and deletes to a staging table(s) and after the Dataflow Task, use a set-based update or delete in an Execute SQL Task. Look at Andy Leonard’s Stairway to Integration Services series. Scroll about 3/4 the way down the article to “Set-Based Updates” to see the pattern.
Stage data
Set based updates
You’ll get much better performance with a pattern like this versus using the OLE DB Command transformation for anything but trivial amounts of data.
If you are into third party tools, I believe CozyRoc and I know PragmaticWorks have a merge destination component.