how do I recover my photos on Iphoto that is no longer suported?

You can open the iPhoto Library in Photos. This will create a new library. from the iPhoto Library, and you can access all photos, videos, albums in this new library. Notes on Migrating an iPhoto Library from iPhoto to Photos for Mac

To open the iPhoto Library double-click it and select to open t in Photos. Or drag the iPhoto Library onto the Photos iCon in the Dock.

Alternately, hold down the options key ⌥ while double clicking the Photos icon. Then select the iPhoto Library in the library chooser dialog.

Here are some additional user tips from Photos for Mac  User Tips that will help you in your transition from iPhoto to Photos:

How to prepare the Photo Libraries before upgrading to Catalina - Apple Community ➙ read first 

External Editors in Photos Are Here

Photo Editing Extensions for Photos for Mac

Post 9/30/2018 Printing Options for Photos - Apple Community

Ordering Books and Calendars on a Mac that cannot be updated past El Capitan 

Use Project Extensions to order print products in Photos after September 30, 2018 - Apple Support

Create and order print products in Photos with Project Extensions - Apple Support