Describe how the arabs created a trade empire. then, identify the items traded in the empire and where they came from.

The main, and most profitable,commodity was slaves. They came from everywhere the Arabs had conquered. 
The Arab slave trade was such that,by the early 9th century, armies of the Arab Empire and some other Muslim states was composed largely of slave soldiers called ghulams,which came from all over the empire. and thats before you start looking at how many slaves were needed for unskilled labour,construction projects, and household roles.

Ammianus