You will get some .psd files that were designed at @1x, you can copy some elements from there to new screens, status bar, some icons and so on. Will provide .sketch files if needed.
... It is not just a "resize" work, you should pay attention to every pixel, font size, line height, all strokes should be resized, icons should be pixel-perfect and so on.
You should tell me approx time and budget for this work, be ready show your experience.