You have to disconnect the line from the breaker and connect this to it so if you are not comfortable opening your panel and taking the line off the breaker, then this won’t be an option.
Also, I’m not endorsing this product, I’ve never used this one in particular, but it looks like the cheapest one that might possibly work for that depth… it says it detects up to 1 meter. Usually residential lines going to detached buildings are 24" but I’ve seen them deeper and I also have seen them barely scratched into the dirt a couple inches too, just depends on the contractor that put it in when your building was built initially.