CSHARP

Convert vector3 to Quaternion Unity

using UnityEngine;
public class rotation_demo : MonoBehaviour
{
    Quaternion rot;
  
    void Start()
    {
        rot.eulerAngles=new Vector3(45,0,90);
    }
}

get quaternion from vector unity

Quaternion rotation = Quaternion.LookRotation(Vector3 forward, Vector3 up);