Get-ADUser -Filter * -Properties LastLogonDate | Select name, LastLogonDate | Where-Object { $_.LastLogonDate -lt (Get-Date).AddDays(-30) }
PowerShell – last 30 days logged users

Get-ADUser -Filter * -Properties LastLogonDate | Select name, LastLogonDate | Where-Object { $_.LastLogonDate -lt (Get-Date).AddDays(-30) }