how do I migrate ALL my iPhoto pictures to Pictures in Catalina???

If you have several iPhoto Libraries, you have to migrate each one of them separately to Photos. Once Photos has created Photos Libraries from them, you can seicht between libraries by quitting Photos and then double-clicking the library you want to open.

On Catalina you can co longer migrate very old iPhoto Libraries, that have not yet been upgraded to iPhoto '09 or iPhoto '11, because the iPhoto Library upgrader tool does no longer un on Catalina. Photos can migrate iPhoto '09 or iPhoto '11 libraries, but not any of the previous versions. That can only be done on a Mac running macOS 10.14 Mojave or an older system version.

You can migrate to an iPhoto library to Photos very simply:

Hold down the option (or alt) key and launch Photos. From the resulting menu select 'Choose Library' and point at your iPhoto Library. It will do the rest.