sunnyday

Hello, I am trying to make a 24 x 36 poster using paint.net I've been using paint.net for years but never for anything this large. Is this possible? I am going to put text in the middle and it will be surrounded by very high resolution images. What canvas size would my project have to be to set this up. Also, if I set up my project for 300 pixels / inch is that the same as 300 dpi? Thanks for any input.