Preferences > Units & Rulers
You can set defaults there.
Note that Photoshop tend to remember the last used setting. However, if your preferences are set to use Pixels/Inch then it should default to that for new documents. Unless, you are using a non-US version of the app. Then it may default to cm.
You can not increase an image's PPI while maintaining it's width and height and maintain quality at the same time.
To determine the physical size of an image at print resolution, divide the image's current pixel width and pixel height by the output DPI.
Pixel width / Print DPI = print width
Pixel height / Print DPI = print height
So, for a 2448x3264px ...