Does urine drying on clothes make them pure, especially if there is no water available, or if the urine consists of scattered drops on the clothes whose exact location cannot be determined?

Clothes are not purified by the drying of impurity, whether water is available or not, and whether the location of the impurity is known or not. If the location of the impurity on the garment is hidden, every place that is likely to have been affected by the impurity must be washed. So, if its direction on the garment is unknown, the entire garment should be washed. If its location is known to be on one side of the garment, that entire side should be washed.