View current users in legacy pool
Before learning the various ways you can move users between pools, we must first determine which users exist in the legacy pool. The Registrar pool column identifies users who are configured for the legacy pool. These are the test users we move to the Skype for Business Server 2019 pool.
To see the list of users in the legacy pool
Sign in the legacy Front End Server with an account that is a member of the RTCUniversalServerAdmins group or a member of the CsAdministrator or CsUserAdministrator administrative role.
Open Skype for Business Server Control Panel.
Select Users, select Search, and then select Find.