As I’ve said many times before, I don’t understand why someone would prefer to use Markdown over Org mode but there are such people. At the very least you may be working with outlanders who don’t use Emacs and therefore don’t have access to Org. Regardless, sometimes it’s convenient to be able to convert some Markdown text to Org mode.
Charles Choi has us covered. In this nice post he provides a bit of Elisp that will take Mardown from the clipboard, convert it to Org mode, and insert it in the current Org file. As you probably expect, he uses Pandoc to do the heavy lifting. That means you have to have Pandoc installed, of course. Choi also mentions that you’ll need to have the system clipboard and kill-ring integrated but I think that’s been standard for a long time. I don’t do anything special on macOS although I do have save-interprogram-paste-before-kill set to t.
If you sometimes find that you need to convert Markdown to Org mode, Choi’s code is a good way of doing so. The code itself is easy to understand and modify if you need to. As Choi says, you can invoke the function in several ways such was a context menu, a Hydra or Transient menu, a keybinding, or simply by calling it with Meta+x. Unless you find yourself using it all the time, you’ll probably find Meta+x and command completion more than adequate.