Hi,

Please run below command on power shell.

Import-Module ActiveDirectory
Get-ADGroupMember -Identity "GroupName" -recursive  | Export-csv MemberList.csv

Hope it helps you.

Also if you want complete list for all Group, Run below command on command prompt.

Import-Module ActiveDirectory
Get-ADGroup -filter * | Select-Object Name, @{n='Members';e={ $_ | Get-ADGroupMember -Recursive | Select-Object -ExpandProperty Name }} | Export-Csv AllGrpMem.csv