Using Elements 11 I need to resize a large number of images for the printing of my book. Some are 72 Pixels per inch some are 220 pixels per inch. Printer requires 300 dpi. What settings do I use?

Using Elements 11 I need to resize a large number of images for the printing of my book. Some are 72 Pixels per inch some are 220 pixels per inch. Printer requires 300 dpi. What settings do I use? Do I resample or not? Do I constrain proportions or not?

AND once you all help me figure THAT out, is there a faster way to do this than to open each of the hundreds of images store in Dropbox, make those changes, and resave them to Dropbox?

Thanks in advance, my publication deadline is crushing me!