All physical moves use the attack stat, all special moves use the special attack stat.
In generations 1-3, moves used attack or special attack depending on their type.
Physical: Normal, Fighting, Poison, Ground, Flying, Bug, Rock, Ghost or Steel.
Special: Fire, Water, Electric, Grass, Ice, Psychic, Dragon or Dark.
From Diamond/Pearl and onward each move is individually physical or special. Check the moves in your game (or on this site) to see what category or type they are.
For your specific ones, you should train attack for all except sludge bomb. But for milotic you should use a special move like surf.
