*Be sure to use the indices to help you search for your topic.
I found several of the trade route/topics here.
If you are struggling to find information, try doing an Advanced Search using multiple "keywords" connected by "and" to refine your parameters.
[and] "Trade Routes" [keyword]
*Note the bracketed words indicate the dropdown choices for Advanced Searches.
*The quotes around "Trade Routes" ensure resources are only selected if the words Trad and Routes are together and in that order.
Google Images looks to be a good resource for images of routes. Notice when you link here that there are colorful boxes which allow you to narrow down your search (Ancient, India, Mongolian, Sarharan,...).
*These could be helpful. Just be sure to investigate the source to be sure it is quality.