Depending on whether your changing hoses bank on 30 ounces and even though it might sound like overkill you can use the discount code at advance and get a gallon of Valvoline for $21, or Pennzoil for not much more at AutoZ. It never hurts to have extra fluids around and hydraulic fluids have a great shelf life.
I recently changed out the steering box, pitman, idler, power steering pump, hoses, belt etc on my GM truck and I had a fresh but open gallon of that before the work was started and there's still a good bit in the jug.

 

1,3 litres.
Dexron 3 (i have change for dexron 6).

 

Dexdron 6 ? Are you sure ? I found atf 134 from mercedes it's the same colour amber . Dexdron 6 is red . For european owners ac delco fluid price it's too much expensive . For 1.2 liter about 60 euro more shipping cost 18 euro from Germany

 

My 07 Owners' Manual shows to use GM part #89021184. However bet that would cost highly in Italy. You might search "gm compatible power steering fluid" or fluid meeting 89021184 specs and see what's available.

 

Problem is that anywhere i not found the same spec

 

I would add fluid until it is between the bottom of the dip stick and the hot mark. Then run the engine for a few minutes and add more fluid as needed. You may want to repeat this a couple of times.

 

After turning the wheels back and forth to their limits to bleed out the air pockets.

 

Thanks JoJoJr, you are correct. I should have added that.