How do I get my photos from iPhoto? Since I "upgraded" to MAC OS Catalina, I can not access my photos. Please help.

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

How to prepare the iPhoto Libraries before upgrading to Catalina - Apple Community ➙ read first if you haven't upgraded to Catalina yet 

Notes on Migrating an iPhoto Library from iPhoto to Photos for Mac 

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

iPhoto was obsoleted years ago, and replaced by Photos. If you open Photos, it should attempt to import your iPhoto library after which you can delete the old library or keep it around.

You need to Launch Photos with the option key held down so that you can choose your iPhoto Library.