How do i determine the value of $l$ and $M$ of the defined ellipse in the below problem?

Question

let an ellipse defined with the following equation :$$ly²+3x²=M $$ and it's center is the origine and intersect with the parobola which is defined with this equation :$$x²+\sqrt{3}y-3=0$$

My Question here : How do i determine the value of $l$ and $M$ where it's periphery is $14\pi$ ?

Thanks for any help