How can I retrieve pictures in iPhoto?

Photos for Mac is the successor to iPhoto and can open your iPhoto Libraries.

Try the following:

• Drag the crossed out iPhotos.app onto the Photos icon in the Dock.

Then Photos will open your most recent iPhoto Library and create a new Photos Library. You can access your photos and albums this way.

If Photos should come up with an empty library, you may have to select the library manually.

• Quit Photos, if it is running, hold down the options key ⌥, then double click Photos to bring up the library Chooser dialog and select your iPhoto Library.

To get you started with Photos, see the user guide: Photos User Guide for Mac - Apple Support

• Updating from iPhoto to Photos for macOS – Apple Support
• How Photos handles content and metadata from iPhoto and Aperture - Apple Support