Welcome to the forums @Nyssa!
To spawn multiple instances, I would suggest using a for loop, and then spawning the sticks using that loop. You can also apply an offset in the loop, so all the sticks are not on top of each other (optionally). Something like this:
func kill():
var number_of_sticks = round(rand_range(3, 7))
for i in range(0, number_of_sticks):
var stick_instance = sticks_scene.instance()
get_parent().add_child(stick_instance)
stick_instance.global_position = global_position
# optional: add offset
stick_instance.global_position += Vector2(rand_range(-64, 64), rand_range(-64, 64))
print ("Stick ", i, " made!")
