Where do the words "Anxi", "Weicheng" and "Yangguan" in the poem "Send Two Ambassadors to Anxi" refer to?

Anxi, the capital of Anxi, was ruled by Qiuci (now Kuqa, Xinjiang) Weicheng: Xianyang County was located in Qin Dynasty, renamed Weicheng County in Han Dynasty (Hanshu Geography), and was under the jurisdiction of Xianyang County in Jingzhao Prefecture in Tang Dynasty, located in the northeast of Xianyang City, Shaanxi Province, on the north bank of Weishui. Yangguan: the name of the border pass set by the Han Dynasty, so it is located in the southwest of Dunhuang County, Gansu Province. In ancient times, it was the same pass as Yumen Pass. The cloud of Yuanhe County Records is called Yangguan because it is in the south of Yumen.