how we can open and publish old cp files into captivate 2019

You simple will not be able to open them in CP2019 for many reasons:

• They date from before version 5, where only the most recent AS version was accepted and probably use a very old AS version.
• Updating is allowed only over maximum 2 versions, and even in that case some functionality may not work. Supposing your cp-files are made with CP4, you would need to update first to CP6 (which will not be functional on Win10), then to CP8, and probably first to CP10 and then to CP11.5. Each time you would need a lot of work to make the update fully functional.

It is just a waste of time. Recreate those projects. If they don't have lot of interactivity and you find an old browser to play the output, you could capture them with Video Demo while playing. Output will be passive video (MP4) but you can use Captivate to convert to interactive video, adding Knowledge check and Content overlay slides.

I doubt that you'll be able to use the library as external library for the assets, as is possible for projects created from CP5 on.

Have a look at this post:

http://blog.lilybiri.com/using-cpquizinfoanswerchoice-for-survey-conversion-from-swf-to-html