how do I access my iPhoto pictures after this is no longer supported by new Operating system?

Use what replaced iPhoto: Photos.

Launch Photos (the multi-colored flower in the dock) with the option key held down. From the dialog, choose your iPhoto Library. Photos will create a new library with your iPhoto media.

Léonie's User tip answers that - and a lot more:

Notes on Migrating an iPhoto Library from… - Apple Community

If I launch Photos and choose my iPhoto library, will my albums in iPhoto be transferred intact or will all my photos be transferred as one total bunch?