Preheat oven to 350 degrees F. Mix 3 cups of water and 3 cups of sugar in a pot. Then heat the mixture on the stove for approximately 20 minutes or until boiled. This will be the syrup.
Then in a bowl mix the almonds, walnuts, pecans, cinnamon powder, nutmeg, cardamom powder, and the rest of the sugar. This will be the filling.
Take the phyllo sheets out and put a little bit of melted butter on each sheet. After you lay about 3 sheets, put the filling in. Make sure you don't put too much. Then lay about another 3 sheets down.
Put the baklava into the oven. When it is golden take it out of the oven and pour the syrup on it.