An example extension for translation of a screen position into a world position for FlxObjects.

SetScreenPosition.hx

import flixel.FlxCamera;
import flixel.FlxObject;
  
//Sets the screen position of a FlxObject using setPosition(which is in world coordinates)
function setScreenPosition(obj:FlxObject, point:FlxPoint, ?camera:FlxCamera) {
	if (camera == null) {
		camera = FlxG.camera;
	}

	if (obj.pixelPerfectPosition) {
		point.floor();
	}

  //scrollFactor if set to 0 would result in the object moving to the screen position in world space
  //So, if the screen was 500 x 500 and the player is at (600, 20) and you use this with a scroll factor of 0
  //the on screen element would move to 0, 0 and not be visible on screen with a width of 500x500.
	obj.setPosition((camera.scroll.x * obj.scrollFactor.x) + point.x,
		(camera.scroll.y * obj.scrollFactor.y) + point.y);
	return obj;
}