Default How can I use SRTM/elevation data for vector layer Global Mapper

I will shortly present my goal: I want to create a 3D model of section of a city. So far the buildings, parcels etc. are digitized, however they do not have any Z/elevation data. Here comes, my question: how could I add height value to vectors using SRTM or ASTER or LIDAR anything with some decency in terms of accurate height values? Is there any way that I could just extract or do some divison or something to get those values for each vector layer in part?

I'm pretty much a GIS and Global Mapper newbie, thus I could use some help.

Best wishes,