Do we need an item number in Fusion to create a parent-child hierarchy for EBS asset migration?

Summary:

Do we need an item number in Fusion to create a parent-child hierarchy for EBS asset migration?

Customer need to migrate asset data from EBS, which has a parent-child hierarchy without item numbers. Do we require an item number in Fusion to create the parent-child hierarchy, or can we create the hierarchy without defining an item number in the asset fbdi import template?