Although I am not using Mandrake (I use RedHat 9), I have spent alot of time on this subject. Hopefully, it works right out of the box for you, but if not, it might help if you look at this previous thread from the hardware forum, where I try and spell out what I had to do to get my USB Memory Key to work.
You do have to mount the device to use it, and a service called 'hotplug' can handle the automatic mounting when properly configured in RedHat and some other distros.
I have heard talk also about a program called 'supermount' or something that is likely included with Mandrake Linux that may also perform the function in place of hotplug, though I have no actual experience with it.
If you wish to mount the device manually, you probably need to do the following:
1. Find out the device it is assigned to (/dev/mouse, /dev/cdrom, etc.). You can usually do this by looking at the output of the program 'dmesg' run from the command line. For most, the USB Key is actually considered to be a SCSI device, and is assigned to '/dev/sda1' or something similar (I would guess depending on how many other scsi devices you have).
2. Find out the filesystem on the USB device you want to mount. The USB Memory Key I bought was a Lexar USB JumpDrive, and it was preformatted for fat32 (vfat). I would imagine this is similar in your case.
3. (Note: You may need root privelages to do the following) You can mount the device using the 'mount' command. You need to know where you want to mount the device (i.e. what directory), and create the location if necessary. Then you should be able to mount it with:
mount -t vfat /dev/sda1 /mnt/flash
The -t option specifies the filesystem (in this case vfat). The '/dev/sda1' is the device assigned to the USB Key, and '/mnt/flash' is a directory name where I wanted the filesystem mounted to.
Your options may be different, and if you're confused, type 'man mount' on the command line to see the manual pages for this command.