"HAPPY DAWN MORNING" appears to be a combination of words and phrases that does not form a coherent English expression. "Dawn" and "morning" both refer to the early part of the day when the sun rises, but combining them in this way does not create a standard English phrase.

If you meant to convey good wishes for a happy morning as the day begins, you can simply say, "Good morning," which is a common and appropriate greeting to wish someone well at the start of the day.