If you haven't discovered how to do this yet already (sorry I'm late), you will definitely want to use the export of the reqPro project and then the "Import ReqPro Project" function in Doors (assuming you are talking about DNG, so please disregard if not as I have no idea if that functionality exists in regular Doors). The reason you want to use the export/import is the linking. However, be forwarned that DNG will create attributes and artifact types for any types you are importing that do not match the DNG project (I am thinking of how ReqPro made every step of a use case a use case of its own, ugh). I would recommend capturing the smallest bundles of requirements you can (while maintaining traceability) and export teach bundle as a project, and then import one by one. Good Luck!
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