Commands in package can i find or show the items , command or everything you call it in a package ? like SpeedOfLightInVacuum in PhysicalConstants.jl
(by the way what do you call them ?)

I am not sure I understand the question, but you may be looking for names. See its docstring for various options.

I don’t understand the question either but one other option to achieve something that might be close to something that someone might conclude from your question you might want to do is:

julia> using PhysicalConstants

julia> PhysicalConstants.</TAB></TAB>
@constant          @derived_constant   CODATA2014          CODATA2018          PhysicalConstant    _constant_begin     _constant_end       _constant_preamble  _name               eval                include

to be clear, just typing PhysicalConstants. (notice the dot) and then pressing tab twice gives the displayed result.