You need to create a workflow to migrate data from the Spoke Orgs to the Hub Org. You can create this workflow by using Informatica Cloud Services or any other data integration tool.
The following image shows a sample mapping created in Informatica Cloud Services to migrate accounts from a Spoke Org to the Hub Org:
The following image shows the continuation of the sample mapping to migrate accounts from a Spoke Org to the Hub Org:
The following image shows the continuation of the sample mapping to migrate accounts from a Spoke Org to the Hub Org: