I have my GPA in the 100 point system, how could I calculate it in 4.0 point system? I searched, and I didn't find a good answer,
You should ask your university if they could provide a mapping to a 4-point system. If they don't, you simply have to calculate GPA*4/100! In case you feel this undermines your prospects, ask your university for a rank certificate which will give the admissions committee a good idea of where you stood in your department.