It is true that we do not know where the Cohors III Thracum Syriaca was stationed, but the other units in the series of four bearing this title all appear in the East.
Apocrypha Syriaca Sinaitica, being the Protevangelium Jacobi and Transitus Mariae, from a Palimpsest of the fifth or sixth century.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "syriaca" in a variety of sentences. We hope that you will now be able to make sentences using this word.