I bought this book , Kindle version but I don't have a kindle I want to change the format to PDF to read easily on my PC. But how do I get the azw or mobi file of it?
You can install the free Kindle for PC software to read it on your computer.
Your book would be saved in the My Kindle Content folder in the Documents folder. Use Calibre software to convert it into the format you require. It is freely available.
I tried that .. the new Kindle version is saving as KFX file which is I don't know how to convert .. the older Kindle version is telling me to upgrade the version if I wanna download that book
You need to install DeDRM Plugin by Apprentice Elf, in the Calibre before importing the book. That way you may be able to open the book in Calibre and save/convert the file in desired format. The main software Calibre and its plug-ins are freely available. Just google for them.