I don't know why because if I format under OS 3.1 I have on the workbench the icon DF2:
? DF3:
? and when I install OS 3.9 I have DF2:Unreadable DF3:Unreadable.
Just a small thought here: are the icons called DF2/DF3 or DH2/DH3? In that case it's just 2 harddisk partitions that need formatting (yeah, sounds stupid but I've had that myself in the past with unformatted partitions on a removable device - took me a few minutes to figure that one out :-))