Can I retrieve photos from Aperture on new iMac?

Which system version is running on your new Mac?

Any Mac with macOS 10.15 to macOS 12 can create Photos Libraries from Aperture Libraries (but the Aperture Libraries have to be converted to Aperture 3 libraries). It will preserve the albums, folders, and projects and keep the edited versions paired with the originals. Then you can use the Photos.app to access your photos and to migrate them to another professional DAM, Lightroom or similar.

On macOS 13 or later it is no longer possible to migrate an Aperture Library to a Photos Library. That window of opportunity has been closed. All we can do no with native Apple apps is to import photos from an Aperture Library into a Photos Library. This will import the media, but not the structure of the library. And it does not handle large libraries gracefully. Even with a moderately sized Aperture Library of just 100GB I got a warning of running out of system memory, when I tried to import the photos from this library to Photos.

You may want to prepare your old Aperture Libraries for the migration on your old Mac with your Aperture 3.

• Most important: Ensure, that all items in your Aperture library are having high resolution preview images. Your Aperture edits can only be migrated by the previews. So let Aperture render high resolution previews to save your work.
• Then use Aperture to export smaller, partial libraries from your large Aperture Libraries, if you can find some useful way to split your libraries thematically or chronologically.
• And use your old Mac to convert items in a legacy format to a format that will be supported by the system version on your new Mac. Audio files need to be removed completely. I had a lot of trouble to track down the audio files I had imported to Aperture for slideshows. These files caused background processes in Photos to hang or crash. When in doubt, if a video or image format is supported on your new Mac, copy it to the new Mac and try to import it to Photos. If Photos refuses to import this file, convert it on your old Mac to a supported format.

You don't need Aperture 1 & 2 if you have 3. It will open any Aperture library.

Now you have to decide what you're going to do - eight years after everybody else - when your other Mac dies. What app are you going to replace Aperture with?