This article explains how to find the service tag of the MX I/O switch modules in MX7000 Chassis via GUI (OME–Modular web interface)
Log in to OME–Modular web interface.
You can find the details of service tags and IO ports of switch modules by browsing to OpenManage Enterprise Modular> Devices> I/O Modules
You can also retrieve the service tag information from IOM Page.
Click on the desired IOM name. It will populate the IOM page. On the IOM page you can see the service tag