In Firefox 50.1, Firebug is no longer available so I have to use the inspector but I cannot find copy ---> xpath option that was available in Firebug. How can I find the xpa
You can't, firefox's inspector does not have such feature. However it does offer css selector which can be converted to xpath with various other tools.
It should be noted however that these generated selectors (xpath or css) are not accurate or reliable and you should avoid using this feature for anything but rare edge cases.