Hi Alex,
From what I gather, you were using AD to create users in the Past. With IdM now replacing AD, you have to create users from IdM. I understand that there is no standard functionality in IdM to copy an existing user to a new users.
Are you looking to copy User/Identity within IdM ?
You can have a look at this blog which explains how to copy roles/privileges from one user to a new user (which has been already created in IdM). You would have to do something similar.
Cheers,
Murali.