dpi applies only to prints, it is meaningless for an digital file.
if you want to render something to be printed at 300 dpi, take the dimension in inches and multiply by 300. That will give you how many pixels it has to be in that dimension
If you are placing your images in a page layout application or the like just scale them to 24% of “actual” size, assuming the application assigns 72PPI to untagged images (which is what DS produces - the 72, or 96, reported by your editor is an assignment when the image is opened or imported).
