Hi. I'm Brian and I'll try to help.
Amazon dropped the support for the legacy Kindle app on Windows as of June 30, 2026. The supported Kindle for Windows app requires Windows 11, according to the Microsoft Store, but have you tried to install it? Does it complain? Why not just use Kindle for Web at https://read.amazon.com/kindle-library? Then it won't matter what version of Windows you use.