您可以在新AAD中将用户添加为来宾用户.

You can add the users as guest users in the new AAD.

您可以通过门户手动进行操作.我听说曾经有一个批量上传功能，但是如果没有，我确定您可以编写一个Powershell脚本来实现.

You can do that manually through the portal. I heard once there is a batch upload feature but if not I'm sure you can write a powershell script to do it.

https://portal.azure.com/#blade/Microsoft_AAD_IAM/CompanyRelationshipsMenuBlade/ExternalUsers