Is there a way to upgrade from 3.0 to 3.5.1?

I upgraded to El Capitan and cannot access my Aperture libraries contained on external drives any longer. I installed 3.0 on an old Mac, but it won't open the libraries either, because they were created using 3.5.1. I can't find a method for upgrading. Am I out of luck? Can Photos open the libraries without importing them (they are too large to import to the computer hard drive)?