Resizing vertex to exact dimensions

Hello there guys. I have no clue on how to use blender whatsoever, im currently modding a game called NBA 2k17 using blender

now my question is lets say i click on a vertex group select the dimensions how do i get the exact scaling for something else in another vertex group? heres a picture of what im talking about.

Now i have a second blender open (Which is the one i wanted to be scaled) and i want the exact dimensions of scaling as the picture in the first post how do i go by that? heres the second picture.