FreeCAD writes out a .geo file after hitting [Apply] button from task panel "Fem mesh by Gmsh"
In report view something like this appears:
Please note red marked text, here you will find generated .geo file
On the other hand your Gmsh.exe is a outdated build from 2016!
We are going to start Gmsh FEM mesh run!
Part to mesh: Name --> Box, Label --> Cube, ShapeType --> Solid
CharacteristicLengthMax: 1e+22
CharacteristicLengthMin: 0.0
ElementOrder: 2
ElementDimension: 3
c:\users\aio\appdata\local\temp\Box_Geometry.brep
c:\users\aio\appdata\local\temp\Box_Mesh_TmpGmsh.unv
c:\users\aio\appdata\local\temp\shape2mesh.geo
C:/Program Files/FreeCAD/bin/gmsh_3.0.6.exe
Group meshing for analysis.
Empty reference: SolidMaterial
One material with no reference shapes. No need to make a group for materials.
{'FemConstraintFixed': ['Face1'], 'FemConstraintForce': ['Face2']}
Start: ViewProviderFEMMeshBuilder::createMesh() =================================
0.000000: Start build up 872 face helper
0.000000: Start eliminate internal faces SIMPLE
0.000000: Start build up node map
0.000000: Start set point vector
0.000000: Start count triangle size
NumTriangles:800
0.000000: Start build up triangle vector
0.000000: Start build up edge vector
NumEdges:1200
0.000000: Finish =========================================================
The Part should have a pretty new FEM mesh!
Please update to version 3.0.6
As you can see in these about dialogs:
FreeCAD is build against OCC 7.2.0, while your Gmsh is build against OCC 6.8.0
This is pretty dangerous.