How do you calculate the points for a predictive trajectory line?

I have an orbital object that pulls something down like this

     public void Attract(Rigidbody body)
     {
 
         Vector3 gravityUp = (body.position - transform.position).normalized;
 
         Vector3 localUp = body.transform.up;
 
 
 
         // Apply downwards gravity to body
 
         body.AddForce(gravityUp * gravity);
 
         // Allign bodies up axis with the centre of planet
 
         body.rotation = Quaternion.FromToRotation(localUp, gravityUp) * body.rotation;
 
     }

and then I have another code that shoots something in the opposite direction of where the mouse was pulled and that is the rigidbody.velocity x and y. So how do you calculate based on those two things th puling of the gravity towards a center and the velocity of the object