Start with the country it was shipped from. Google will help you find the postal service website, and most have an English translation.
However, your real question is "where is my purchase and when will it arrive?"
First ask your seller or the date of shipping and the service used. If there is no response or if the response is unsatisfactory, start an Item Not Recieved Dispute.
Now.
It usually takes up to 20 days for an item to arrive within North America.
It usually takes up to 15 or 20 days for an item to arrive from Europe.
It usually takes up to 30 days for an item to arrive from Asia.
Has that much time passed? If not it is too early to be concerned.
If it has, start an Item Not Received Dispute. Do not close it until you have either your refund or the item. You have only 45 days from purchase to do this. Do not allow it to go past Day 42.
Some sellers, usually Asian, will try to persuade you to wait longer. Don't. They should have shipped by a faster service. (In many cases that sentence should read "They should have shipped.")
Tracking is useless to the buyer. It does protect a seller from fraudulent non-delivery claims. Not the buyer's problem. File the Dispute and get your money back.
