Plugin lookup

I have a plugin which reads a file and extracts data from several crm entities to create a new record in a third entity

when I query the lookup field in entity a, I get a string of the id back into the plugin, how do I convert this back to a entity reference to insert in to the new record in entity B

I have tried

Dim LicenceGuid AsNewGuid

Guid.TryParse(ImportReturnElements(2).ToString, LicenceGuid)

but that throes up an exception