How do I retrieve photos from an outdated version of Aperture to iPhoto?

I use a MacBook Pro operating OS X 10.7.5 and iPhoto '11. I inherited this computer when my father passed and found a number of photos he had taken which I created a library and dragged into iPhoto. I also found an Aperture library that won't open. It tells me that it is outdated. It then asks me to purchase the upgrade (which I would rather not do since I don't use Aperture), but it also tells me that the upgrade is not available in the UK (my father lived in the USA). Is there a way to check if there are actually any photos in the Aperture library without having a current version of the program? If so is there a way to move them into iPhoto?