Eternal Happiness in Chinese / Japanese...

永遠の幸福 means “eternal happiness” in Japanese.

永遠 means eternal, eternity, perpetuity, forever, immortality, and permanence.

の is a possessive article which sort of makes this selection mean “happiness, of the eternal kind.”

幸福 means happiness, though this word can be translated as truly blessed, joy, happy, welfare, well-being, or fortunate.

幸福永恆 is a short way to say eternal happiness in Chinese.

Breaking down the parts:
幸福 means happiness, happy, blessed, blessedness, joy, and/or well-being.
永恆 means eternal, everlasting, and/or forever.

Another way to write this is 永恆的幸福. It reverses the word order and adds a possessive article. I prefer the shorter version, which is slightly more natural in Chinese.

永恆和平與幸福 means “Eternal Peace And Happiness” in Chinese.