Add link to admin docs from Migration API (#20317)

data/variables/migrations.yml

@@ -1,7 +1,7 @@
 user_migrations_intro: >-
   You can use this API to review, backup, or migrate your user data stored on {% data variables.product.product_name %}.com.
 organization_migrations_intro: >-
-  The organization migrations API lets you move a repository from GitHub to {% data variables.product.prodname_ghe_server %}.
+  The organization migrations API lets you move a repository from {% data variables.product.prodname_dotcom_the_website %} to {% data variables.product.prodname_ghe_server %}. For more information, see "[Exporting migration data from GitHub.com](/admin/user-management/migrating-data-to-and-from-your-enterprise/exporting-migration-data-from-githubcom)."
 source_imports_intro: >-
   The Source Import API lets you start an import from a Git, Subversion,
   Mercurial, or Team Foundation Version Control source repository. This is the same