For a 2.5 × 3.5 inch print, aim for about 300 pixels per inch for best quality on a small photo viewed up close. That works out to roughly 750 × 1050 pixels (2.5×300 by 3.5×300). Around 200 ppi can still be acceptable, but 300 ppi is a safer target for a small frame.

You usually do not need to change anything in the camera. Shoot at the D3300’s full resolution so you have room to crop and adjust later. More pixels are fine.

The important part is matching the image’s aspect ratio to the print size before printing, otherwise the lab may crop off the edges unexpectedly. A 2.5 × 3.5 print has a 5:7 aspect ratio, so crop your image to that shape in editing software. Many editors let you crop to a set width, height, and resolution, such as 2.5 in × 3.5 in at 300 ppi.

You can then save the file and let the printer or lab handle the final resizing if needed.