To do what?
Depends on which powder, and which loading of the 9mm.
Gun powder was originally a combination of ground saltpeter, ground charcoal and ground sulfur. the original gun powder had problems. one it gumed up your gun, two it produced too much smoke. we now use a much more usefull and smokeless powder i forget the name though...
Whatever the reloading manual has in it.
It all depends on how much you want to purchase and where you buy it.
Black Powder.
In California, individuals without a permit can legally possess up to 5 pounds of black powder or smokeless powder for personal use. However, it's important to check with local laws and regulations regarding storage and transportation of gun powder.
Gun powder is always a mixture.
Depends on the size of the barrel.
Gun powder can be used as a propellant rather than powdered sugar and KNO3 depending on the application. Both are explosive, however gun powder is designed to ignite at much higher speeds.
gun powder was udes for fireworks, then weapons
Depends on which powder is used, and there are several. If using Winchester W748, it would be about 23.5 grains of weight of powder.