If you need to found out whitch groups (mailling groups) a contact is member of in Microsoft 365, then you case use these powershell commands:

$getsessions = Get-PSSession | Select-Object -Property State, Name
$isconnected = (@($getsessions) -like '@{State=Opened; Name=ExchangeOnlineInternalSession*').Count -gt 0
If ($isconnected -ne "True") {
Connect-ExchangeOnline
}

$dn = (Get-MailContact "[email protected]").DistinguishedName
Get-Recipient -Filter "Members -eq '$dn'"

Replace [email protected] with yours mail address.