I upgraded my MacBook Pro to Ventura and cannot import an iPhoto library that was organized under Monterey

Converting iPhoto or Aperture Libraries to Photos Libraries is no longer supported in Ventura. macOS 12 Monterey has been the last system version to support it. I have kept my older macs on macOS 10.14 Mojave to be able to work with my older libraries.

But on macOS 13 Ventura you can import directly from iPhoto Libraries, as the message you have seen told you to try.

Try the following:

• Launch Photos, if it is not running and open the Photos Library, where you want to import your iPhoto photos to.
• Then use the command "File > Import" and select your iPhoto Library in the Import dialog. Then click "Review for Import".
• Photos will now show you a list of new photos, that have not yet been imported to this library. Click "Import all new Photos" or select the photos you want to import.

You need to use an earlier MacOS to convert the iPhoto library to a Photos library. Or the alternative in the message you quoted.

The iPhotos library is a package. You can open it in the Finder and see what's there (Show package contents)

import should allow you to import the photos from the iPhoto Library, unless you are keeping the iPhoto Library on an external volume, that is no longer compatible with Photos on Ventura. But as long as the iPhoto Library is in your Pictures folder it should work.

But if you have a mac with an older system version, why not convert the iPhoto Library to a Photos Library on the older system? This way you can save your albums and folders, not just the photos. Exporting the photos from Photas and reimporting in another library is the worst solution, as the originals and the edited versions will no longer be paired and you can no longer revert the edited versions to the original.