/my/preferences/account is not public; other users cannot see that, but based on your use case, it might be enough for the user themselves to see their ID.
You need to find a plugin outlet that is close to where you want to show the information. I usually use the button in the developer toolbar to make them visible on a forum. Seeing them within the forum makes it easier for me to find the best outlet. You can find more information on how to show something in an outlet in the Theme Developer Tutorial: 1. Introduction