There are many more than 50 statues in the game and all of them are located in Orchard, Estate or the Sewers. In Estate, a lot of them look like busts on tables, so make sure you hit those. You'll know that they are the right ones because it'll give you a screen notification (middle-right) telling you how many "statues" you've destroyed.
You will see one in front of you at the start of chapter 9. Make sure to check ALL corners of this area before you leave it. There's a lot here. In chapter 10, you will be inside the mansion and there will be a lot of statues and busts to break here too.