I'm not really sure what you are looking for here or what the Islamic calendar is all about, but just to get the conversation started, are you looking for a way to just display the date as such?

If so, the formula for D1 should be: =a1&"-"&b1&"-"&c1

...keeping in mind though that this will only be recognized as text by Excel.

Otherwise, here is an article that explains how to format Islamic calendar dates.