To download a specific NPM package, you need to dowload the related module from ABP Suite. There's no list of all NPM packages!
See also https://support.abp.io/QA/Questions/632/How-can-I-download-the-framework-and-source-code-for-pro-modules#answer-70bbbda7-c0a0-6b02-f782-39f93f11167d