1. Are you migrating the whole database( user, groups,. posts and all). I will suggest moving the database and using https://cs4you.net/ to update the urls. this works great.
2. Or If it is going to be a new install, you can simply export the tables from the first install for user/groups and import them in the new install
Or if all you want is use the new theme, you can simply upgrade the install.
