just to be sure you understand what you have to look for
the dpi should be at least 150 for print and 300 for press (you got that)
the document size will then reflect how big the print will be
the pixels are how many pixels are in the picture = they are connected to dpi and document size, so if you raise the dpi but keep the document size, the number of pixels will increase, if you raise the dpi but keep the number of pixels, the document size will decrease