How I can Converting a Direction Vector to Quaternion rotation?

I'm fuzzy about what you are looking for here. Say you have a cylinder that is on a surface and parallel to a normal and you move that cylinder to a now position on the surface so you want align with the new normal, you can do:

 transform.rotation = Quaternion.FromToRotation(transform.up, hit.normal) * transform.rotation;

Backing off to what you ask for specifically, you need a reference vector. You need to define what represents zero rotation for that vector. So if you are talking about a terrain in which flat is Vector3.up, you can get the rotation:

var q = Quaternion.FromToRotation(Vector3.up, hit.normal);

'hit.normal' is the normal of the surface. Typically it is acquired from casting a ray.