How can I get to my Iphoto pictures since the Catalina upgrade

iPhoto is no longer supported on Catalina, because it uses some 32bit code, that is not compatible.

There will probably be no update for iPhoto. The last update for iPhoto has been released early 2015, when Apple stopped the developement of iPhoto and replaced it by Photos for Mac.

Use the Photos for Mac application to open your iPhoto Libraries.

Launch Photos while holding down the options key ⌥. Release the key, when the library chooser dialog appears and select your iPhoto Library to open.

When Photos opens, you should be seeing all photos and albums as described here:

How Photos handles content and metadata from iPhoto and Aperture - Apple Support

Then try to find another application to replace iPhoto, if you do not like Photos, but it will give you at least access to your photo libraries.

Some background information: Notes on Migrating an iPhoto Library from iPhoto to Photos for Mac

Photos does not merge libraries. After you open one library in Photos, then migrate another library, Photos will create a new migrated library. Give each of your iPhoto Libraries a unique name, before you migrate them, so the new Photos Libraries will also have different names. You can switch between Photos libraries by double clicking the library you want to browse.

This Help page explains how to handle libraries in Photos: Create additional photo libraries in Photos on Mac - Apple Support

You can merge the Photos Libraries by exporting the photos from one library and importing them into the other library, if you want them all in the same library, see: Notes on Merging Photos Libraries, 2019 V… - Apple Community