What is my purpose in life?
Quelle est ma raison de vivre?
My purpose in life is être heureux
If you want a translation I’d say “Quel est mon but dans la vie?”. If you want an aswer to your question, I don’t know but there are many possibilities 
What is my purpose in life?
Quelle est ma raison de vivre?
My purpose in life is être heureux
If you want a translation I’d say “Quel est mon but dans la vie?”. If you want an aswer to your question, I don’t know but there are many possibilities