How do I know what kind of capacitor I need to buy for my A/C unit, it has 3 wires attached to it? Is this a single or dual capacitor?

A single capacitor has two post coming out of the top of the capacitor and each post has four spade clip terminals.

A duel capacitor has three post coming out of the top of the capacitors and each post has four spade clip terminals. Also the duel will have imprinted on the top the letters "Fan" "Herm" and "Com".