Not used iPhoto for a while now.The question mark usually means that iPhoto can't find that photo in the Library. Is this your Mac? If so were photos added to the Library when you imported them?
If you open the image and see the exclamation mark try selecting Photos from the menu bar and click on the dropdown that says "Revert to original".
If that fails, you can go into the iPhoto Library file in Home Folder>Pictures and drag the photos out from there. You'll need to select the Library file and then Right, or Ctrl click and then choose "Show Package Contents".
There should be folders called Originals and Modified. Your photos should be in those. If you've edited any, the edited versions will be in the Modified folder, with all original and unedited photos in the Original folder.