Get all CONVERT(datetime) styles (formats)
There is no such built-in function – or system table, or view – that would give you a list of all styles (formats). Otherwise people would not have been creating custom-made style lists (like this one, for instance) – as a way of a reminder, I guess, because the same information can be found in the online documentation, even if slightly differently arranged.

Go ahead and create one for yourself. New styles are sometimes introduced with new major releases, but those do not happen too often, so maintaining such a list should not be much of a burden.

Another thing is whether you really need to have such a table. Unless you are still using a pre-2012 version, you can format your datetime values arbitrarily with the FORMAT() function.