You might not have much luck there i'm afraid,

The A/V Out is for sending audio and video out of the camera, (hence the name). Sometimes the same socket is used for input too, but it would normally state that (A/V In/Out).

It's also worth noting that if the camera does have the facility to record from an external mic, you would normally need to turn it on in the cameras record settings menu. Would be worth checking your cameras menu system just in case.