The answer to your question is hindiusim
The trading route most likely happen by ships through the Mediterranean Sea.
The only option besde that would be by land. But the distance required to do by land is further than those the sea and it has to pass the territory of Greece and Turkey, which will guarantee additional toll payment and reduce the traders' profit.
After studying the maps that you posted with the question, the map that shows both the dominate air pressure over India can be found easily. So the air pressure system that forms in the summer and the direction of the surface winds around the air pressure system can be found in map number 1.