What can be wear around your neck and it has six strings and could be plugged in?

What you're describing sounds like an Electric Guitar, particularly if it's designed to be worn around the neck like a necklace or accessory. Electric Guitars typically have six strings and can be plugged into an amplifier. However, if you're referring to something more wearable, it could also be a playful interpretation of a miniature guitar or a decorative piece that resembles one.