MoveTowards

transform.position =
    Vector3.MoveTowards(
        transform.position,
        objetivo.position,
        velocidad * Time.deltaTime
    );

Detectar llegada

if (Vector3.Distance(
    transform.position,
    objetivo.position) < 0.1f)
{
    Debug.Log("Llegó");
}

Resumen rápido

Vector3.MoveTowards(...)
Vector3.Distance(...)