Any decent 3D DCC (Digital Content Creation) application has powerful and effective scale tools - Blender, Modo, Maya, C4D - each has its own unique workflow and quirks.
Instant Meshes would help you retopologise those point clouds into viable meshes for use in most 3D model contexts (editing, printing etc) and will save you huge file size too. I'd probably do this step prior to trying to scale massive meshes to be the same scale; this will allow you to select analagous points on your two meshes to align and scale - as raw point clouds, you have no ability to correctly locate the correct points for such an operation.
You might also consider importing your point cloud into a CADD or BIM app if you have any of those available to you - or for free but effective CAD you could look at Onshape,FreeCAD, or Draftsight.
All of these will support explicit target scaling methods.