I am a beginner to automated testing. I cannot find Firebug and Firepath on Firefox add ons. so What are the alternatives to FirePath and Firebug with the Firefox?
Essentially the functionality is now present in Firefox.
The official advice is to use this: https://developer.mozilla.org/en-US/docs/Web/API/Document/evaluate
You can read about that here: https://hacks.mozilla.org/2017/10/saying-goodbye-to-firebug/
Where they note:
The process of unifying Firebug with the rebuilt devtools was completed with the release of Firebug 3 (aka Firebug.next) in 2015. This prototype was built as an extension to built-in Firefox devtools and eventually integrated directly into devtools. You can learn about how to migrate from Firebug. You can try Firefox Developer Tools by updating your release browser or downloading Developer Edition.
The migration path is detailed here: https://developer.mozilla.org/en-US/docs/Tools/Migrating_from_Firebug
Alternatively You can use Chrome, which like the newer Firefox, has direct Xpath support built in. The search box in the inspector supports Xpath so you can work it out in Chrome and then use it in Firefox as the resulting Xpath should be the same for both Firefox and Chrome. And Chrome as ever supports right clicking on an element and you can then "Copy as Xpath". But those generated Xpaths are brittle, so avoid.
Fundamentally the best thing to do is to learn about Xpathsm then tools like Firepath lose most of their value: https://www.guru99.com/xpath-selenium.html