I don't quite understand what you are trying to say but I will just find the length of all the sides for you.
We know that AB is three times bigger than DC.
Because the triangles are similar EF is three times bigger than GH.
GH = 6 cm
So... EF = 6 x 3 = 18 cm.
We can also apply the scale factor to find AB and DC.
DC = 6 x 2/3 = 4 cm
AB = 4 x 3 = 12 cm
Now we know that the other four sides lengths are the same because the triangle is isosceles.
AD = 8 cm
BC = 8 cm
EH = 8 x 3/2 = 12 cm
FG = 8 x 3/2 = 12 cm