Proud of my dads heritage

I am trying to find my roots back through my dads family, The Procknows. We spelled our name with a change in one letter. Prochnow is how I grew up spelling my name only to find out that it was originally spelled Procknow in Germany. I want to find out in what part of Germany and Prussia my dads family came from and who my relatives are. My grandmas family name is Popplow. I cannot find any information on this family.
My dad just passed away and I want to follow his roots because my dad and grandpa were such inspirations to me. I never knew my grandma but wished I had. I have found old passports and am trying to find out how they arrived into America, by what means and when. I have heard they arrived as children and would like to follow their lives so mine can be much richer. I live in the house my grandpa, my dad, and I and also my children were raised. It would be thrilling to know how my life got to be where it is today!