In the 'Restore' screen, find the first media used.
First, right-click in the left-hand listing pane and make sure you are using "Media View".
The first media used in a job will be listed in the format "Family name(media id)"
(BTW - if you didn't know, this is where the "Family name" setting from a job setup is used.
It can be very useful at restore time if you give jobs family names like "weekly tapes", "daily tapes", etc.)
Right-click, "Properties | Media"
Cheers