It will depend on the version of Aperture that has created the Aperture library, if Photos for Mac can open the Aperture Library or not
If you have been using Aperture 3.6 it should work.
As you do no longer have Aperture, there will be problem, however, if you have used Aperture's ability to reduce the size of the previews. Photos for Mac cannot recreate the adjustments you applied in Aperture, so it will use the previews of the edited versions to migrate the edited versions. If you notice blurry, low resolution pictures after migrating your Aperture Library to Photos, revert any blurry pictures to the original get back to the high resolution original. To migrate an Aperture Library and save the high resolution edited versions, we need to be able to run Aperture and to render high resolution previews of the edited versions, if we do not have already high resolution previews for all edited versions.