Hi @Anonymous ,
Do you mean Azure AD group?
If yes, two ways you can try to get all the members from a particular group.
1. You can use Azure AD connector. Add a dropdown control and set its Items property to below formula:
AzureAD.GetGroupMembers("cdd2bc5c-a5ac-4516-8ab9-740a2b8974a2").value.mail

If you want to show all the user name, you can use:
AzureAD.GetGroupMembers("cdd2bc5c-a5ac-4516-8ab9-740a2b8974a2").value.displayName
2. You can also use Office365Groups connector. Add a dropdown control and set its Items property to below formula:
Office365Groups.ListGroupMembers("cdd2bc5c-a5ac-4516-8ab9-740a2b8974a2").value.mail
If you want to show all the user name, you can use:
Office365Groups.ListGroupMembers("cdd2bc5c-a5ac-4516-8ab9-740a2b8974a2").value.displayName

Notes:
1. Add the Azure AD connector or Office365Groups connector first.
2. Replace to your group ID. You can get the group ID from below "Object Id" property:

Best regards,
Allen