How to import a Revenue Line Item correctly?

Hello Devs, in this ocassion I want to ask you if you can please help me with the following:

I want to import A LOT of Opportunities with their Revenue Line Items, I am importing directly the RLIs so the Opportunities can be created automatically. But whenever I want to migrate the RLIs I can not seem to find the "Unit Price" to connect it with the RLI, and this is making it very hard for me to migrate correctly all the information. 

Please enlighten me if I am missing something here please or if there is a correctly way of doing this. 

Thanks in advance everybody!

Best regards, 

Ángel Ruiz