You will need the fimware for the wasabi as Aldanga has directed you to.
Wasabi only has a connection for Esata hard drives !
If the external USB drives you have are Esata drives you will be fine as a cable is supplied with the wasabi, if your external USB drives are sata drives then you will need to buy a Esata to sata cable.
If they are in a USB chassis/case which sounds like they are then you will have to take the hard drive out the chassis and connect the drive to the wasabi using your cable while using the chassis to power the drive.
Hope this helps.