There are several ways of obtaining the Service Tag from a Dell computer. In order to get it from a local computer, open the Command Prompt and type wmic bios get serialnumber.
To get more detailed information from a local workstation you can use wmic csproduct get vendor,name,identifyingnumber.
However, sometimes you need to get this information about another computer on the network.You can use the below commands to do this. Note that credentials of an appropriate account will be required. In the example below, we’re using the Administrator account, which is commonly used (but shouldn’t as it is best practice to disable it or rename it).
wmic /user:username /node:name_or_ipaddress bios get serialnumber
wmic /user:username /node:name_or_ipaddress csproduct get vendor,name,identifyingnumber