carddisk.device is the name of a driver for RAM cards. RAM! It has nothing to do with CompactFlash. Nothing! Why are you so magically pulled towards carddisk.device when you see it? There is also atapi.device which is similarly unrelated. You never selected atapi.device, so why do you always select carddisk.device?
Connect your new CF card to the IDE bus, run HDToolbox, select scsi.device. s c s i . d e v i c e !!!! If it sees the disk and lets you create partitions on it, then it's compatible, otherwise it's not. That's all.
In order to transfer data from the old CF card to the new one download cfd.lha from Aminet, unpack it and copy compactflash.device to the Devs directory. Connect the old CF card to the PCMCIA bus and run OS3.9's Mounter utility, select compactflash.device (compactflash, not carddisk!!), and mount one or more partitions.