bpexpdate and cleanup

Master - Solaris NBU 7.1.0.3

Media - Red Hat Linux

DD690

Question:  after using bpexpdate to expire images

what do I type next to remove those deleted images from my data domain? because i don't see a change in more free space :0(

I know it's something like >./bpexpdate -m <mediaid> -force and also >./bpimage -cleanup -allclients

but how do i get the media id portion information to input in the command line? 

Thanks again for your help!