Hi,
You are a bit out of luck on this, I would go to Amigakit and see if they have a set of 3.1 disks to buy. I was going to tell you to just pop in the HD and by using the Install command install the OS from there on a newly formated disk, but this won't work since you have OS 3.9 on the hard drive. Your only hope is to buy a set of 3.1 disks from Amigakit.