grammar - What's the difference between three of cups and three cups?

Is there a significant difference between two expressions?
Is it okay to use the former in the context like "I found the three of Holy Treasures"?
I've never heard the former in everyday contexts and I'm not sure if it's gramatically right or wrong. Unlike the phrases like three of us, three of them, or three of hearts as in playing cards, it rather sounds unfamiliar to me.
I want to know if it's possible to use the phrase like "three of somethings" and if so how it's different from just "three something."

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