If left untreated,how long would it take for a bloodclot in the lower leg to travel to the lungs?

If left untreated,how long would it take for a bloodclot in the lower leg to travel to the lungs?
Some blood clots never move, especially if they are in superficial veins. Deep vein clot (thrombosis - DVT) is much more dangerous as it involves the larger veins which have a direct connection to the inferior vena cava and the heart. From there it can go to the lungs (pulmonary embolus) or to the brain/kidneys/intestines if you have a common heart defect called a patent foramen ovale. If you haven't gotten a medical opinion, you should seek one immediately.
It could never happen, or it could happen with no warning, instantly. You really need to get the proper treatment.