How to become admin to particular Yammer network?


We have a tenant in Yammer named let's say and is not in our organization. This is connected to a Yammer network, which should be resolved, since we have to transfer it to our current tenant.
To secure the data before the migration, we need administrative access to
How can we do that?

I read already the article below:

The way I interpret it is that, when I migrate the network, the content will be not taken. It says here that I should first make a backup.

Unfortunately, I am not administrators in or the external networks we create there.

If we have to make a data backup, we need admin rights. How can we do that?