Please try using below -
Get-PowerBIWorkspace -Scope Organization -User "abc"
See available PowerShell commands available in below and open them for examples and more help -
https://learn.microsoft.com/en-us/powershell/module/microsoftpowerbimgmt.workspaces/?view=powerbi-ps
Also it's better if you reach out to experts in dedicated forum for PBI here - PBI_Comm_Forums
===============================================
If the response helped, do "Accept Answer" and upvote it -- Vaibhav