You can follow the status of your packages sent via USPS on USPS’s own website. On the Track page, which you can access by clicking the Quick Tools tab from the homepage, you can enter up to 35 tracking numbers at the same time. (https://tools.usps.com/go/TrackConfirmAction_input)
When entering more than one tracking number, these numbers must be separated by commas. The tracking numbers differ depending on the type of shipment. The formats of these numbers are shown in detail with examples on the tracking page of the site. The tracking number can be found on the invoice, confirmation mail and similar places.
USPS Package Lost
In cases where your package is lost, it is recommended to first check the status of your shipment on the tracking page. Then recommended to create an assistance request first. The relevant form and detailed information are available on the USPS website. (https://www.usps.com/help/missing-mail.htm)
If your package has not reached you within 7 days after your request for assistance, it is recommended to create a Missing Mail Search Request. On the website where you can get information about the request for assistance, the related and subsequent actions are stated.
USPS Customer Services
USPS has shared their contact information on their site. Although there are no messaging services where you can get instant answers, information of many units that can support you has been shared via e-mail and telephone numbers. Details of holidays and the nearest post office information are available on their website. (https://www.usps.com/help/contact-us.htm)