Teams get current list of external conversation before block the external users chat

Question

Hello team,

We are planing restrict the teams external user from allow all domain to specific domains

Microsoft info:

https://learn.microsoft.com/en-us/microsoftteams/trusted-organizations-external-meetings-chat?tabs=organization-settings

Before run this restriction, we would like to have an inventory of the current domains which our users are talking to, if the domain is valid, we will add to the white list,

Do you know how to get that inventory?