You can't;  information isn't customer-accessible.  You must call Support.

I was able to check the dispatch number.  I will include the link to the location where I checked my dispatch number.  https://support.dell.com/support/supporthistory/MiniDispatch.aspx?c=us&cs=19&error=true&l=en&s=dhs&ServiceCall=129257004&ServiceTag=

<ADMIN NOTE : Service Tag removed per privacy policy>

inm is right. Go to the Dell support website, input you service tg # and dispatch # to get your answers. You can also follow your service history as well.

Would suggest inm remove the tag number on his link to the service page.