egag,
While I don't think that mkfs.vfat is available in Slackware 10 (at least it's not available on my full install of SW10), but if memory serves me correctly you should be able to do...
mkdosfs -F 32 /dev/hxx
Just replace the xx with the correct drive and partition where you want to create the FAT 32 file system on. Don't forget to create your FAT 32 partition first!
p.s. If you need more information about mkdosfs you should check out, "man mkdosfs"
p.p.s. Typically filesystems "formatting" is done with mkfs, check "man mkfs"