I want to move objects by mouse drag

The hit obtained from Physics.Raycast() contains the world coordinates hit.point of the point of contact with the ray, so take advantage of this.

Find the value to move the depth of the contact point.

private float depth;

depth = Camera.main.transform.InverseTransformPoint(hit.point).z;

Find the relative position vector from the target object so that the contact point can be picked up.

private Vector 3 offset;

offset = hit.point-this.transform.point;

Reflect these values when you move them.

Vector3 mousePos=Input.mouthPosition;
mousePos.z = depth;

moveTo=Camera.main.ScreenToWorldPoint(mouthPos);
transform.position=moveTo-offset;