The login details are stored in Master DB. I think you will have to query sys tables by connecting to Master DB as shown in below
https://stackoverflow.com/questions/36653699/sql-azure-list-all-logins-and-users/47470806
Get-AzSqlServer PS Command won't list the all the login details AFAIK
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Please don't forget to Accept Answer and Up-vote if the response helped -- Vaibhav