According to Ray :
The previous owner of my home burried some Romex to power up a pool pump and
he ran a branch to a receptacle for a non existent sheded off this to
provide a receptacle to a non existent shed.

I like to do some trenching in my yard to run conduit to a workshop that I
built but want to avoid the existing romex.

Is there a way/device to help me find the burried romex. I tried a metal
detector and after adjusting the sensitivity it still picks up a lot of
stray stuff in my yard and does not give me a clear picture of the location
of the romex.

Some of the "buzzer" suggestions _might_ work, but don't count on it.

[In case it isn't obvious, futzing with the main like that other
stupid suggestion can kill you.]

Call your local power company. If that line is delivering power to
something, they can probably detect it with their equipment. Despite
it not being their main feed, they _may_ be willing to search for it.
Especially if you need them to find your main feed anyway.

[Recently, I did just that. I needed the mains found before some
garden work, and when the guy was onsite, I asked him if he'd take
a quick scan for the buried feeder to the garage which was only a
few feet away and I needed to avoid it too. He spent a few seconds
searching for part of it, found it, I thanked him, and that was that.]
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.