You can open the Physics Debugger via .
If you're trying to debug 3D physics queries (overlap, check, cast) via the Queries tab.
Your version of Unity may not have the Queries tab, you would have to update to draw queries using built-in functionality.
You can visualise collision geometry if it's unclear what's being hit by a query.
You can show collision geometry in the scene by enabling its visibility from the overlay in the bottom right of the Scene view window.
Unity, huh, how?