Have you tried doing a Google search for topics related to market places on the dark web?
even if you try it, I think you will never be able to find it, because google or something pertinent certainly will block that place. but you can find the black market in the deep web, I guess you've heard of it, if not, maybe you should look for its own information
yeah its very hard for to exist dark market place in the internet world( i mean realworld internet ) as its more likely to get caught by opening such service so people target deepweb ( tor ) to open such market places there as due to its anonymity level !