Yes, this is pretty straight forward:

Allocate new minidisk volumes
Format them for ADSM use
Define the volumes to the ADSM DB or Log (and associated mirrors)
Do not extend the size of the DB yet, keep it the size it is
Remove each 3380 volume (ADSM will move the data from the volume being
        removed to other available volumes)
Determine if you want to extend your DB now to take full advantage of the
   new capacity of the 3390 drives

You should take a consistent DB backup before you do this.  All of this can
be done while the server is fully operational.  When you actually remove
the log volumes you may notice some locking going on where other processes
are stalled for a short period of time, but this is normal.

Paul