You chose the file "C:\Users\chaim\Desktop\test3.txt"
-- FreeFem++ v4.7 (Fri, Sep 04, 2020  1:37:14 AM - git v4.7-2-g3716c303)
 Load: lg_fem lg_mesh lg_mesh3 eigenvalue
    1 : load"gmsh"(load: loadLibary C:\Program Files (x86)\FreeFem++\\.\gmsh = 0)
    2 : mesh3 Th=gmshload3("Part1.msh");
    3 : plot(Th,cmm="Th mesh read from GMSH",wait=1);
    4 : savemesh(Th,"Th3.mesh");
    5 :  sizestack + 1024 =1256  ( 232 )
 
edges in 3D mesh are not considered yet in freefem++, skeep data
0 tetrahedrons
0 triangles
1 numElements
 Return type false, your mesh is MeshS type, use gmshloadS function
  current line = 2
Assertion fail : (0)
        line :1037, in file gmsh.cpp
Assertion fail : (0)
        line :1037, in file gmsh.cpp
 err code 6 ,  mpirank 0
 try getConsole C:\Users\chaim\Desktop\test3.txt