How to see the referring domains inside the marketing channel Internal?

[KilvarEK]

I have few sister websites from our main website. If I look at the Marketing Channels I can't see the Referrer Domains if I use for instance Marketing Channel Detail or Referring Domain.

koffiexp.com is our main website and I want to see how many visitors were from our sister website top-x.nl when they converted. What dimension do I use to see the referrers within Internal in Workspace?