Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
You can tell which is which by the positions of stuff like the mixture screws etc for example, if the mixture screw opening is on the right it's either 3 or 4 cylinder, left and 1 or 2 cylinder, after that you can tell which is which by the way certain stuff aligns, stuff like the blanking plugs fitted where the slide pivot pins are fitted. Study them before dismantling and you'll start to spot the differences. As an example, your pics show 2 internal carbs as those have the vent pipe fittings, the one of the left is number 2 cylinder as it doesn't show the mixture screw opening and the blanking plug is showing. The one on the right is clearly the broken one that you replaced as it shows all the same fittings in all the same places
The odd thing about your pic is that the float bowls don't match the carb. The one on the left does as it's drain screw faces the right direction (they face out not in so you can get to them) the one on the right is a float bowl from either 3 or 4 cylinder.
was there one in the spare carb i sent you? i can find you one if you are stuck.