Method 1. Launch a Steam game (Counter-Strike Source, Left 4 Dead, TF2 . . .) and enter status into the console.

Method 2.  Use a text editor (Notepad, Wordpad) to open the file C:\Program Files\Steam\steam.log.  Look for a line that is similar to,

attempting new connection 0,68.142.72.251:27030 for 0:1:88721

Your steam ID looks like the last number, 0:1:88721.