I like to 3D printing this robot: GG96 Robot in small size (about 12*12*12 mm) and want to directly connect rear wheels to a DC motor that I will put inside the down box, but don't know how to connect front wheels(they will be free).

Also I like to put 2 micro servo motors in middle box and connecting the arms to them, but I have no idea about this connections too!

I am not mechanical engineer but like to make robots and know a little solidworks! may you help me about these connections?