Finding a base plane of an InstanceDefinition

Hi everyone,
I’m trying to place a new instance of a block to Rhino document using AddInstanceObject method. It’s required to provide a Transform parameter and I plan to use Transform.ChangeBasis to get my new block in place. But I can’t find a way to get the initial plane for a InstanceDefinition. Looked through all the properties but there aren’t any related to a base point or location.
Please help

My bad…
Need to use Transform.PlaneToPlane(Plane.XY, newLocation) instead of ChangeBasis