I had an Inspiron 400M with which I used a Dell external drive. It has a dual USB connector. The mini does not have this type port.
Any way to connect it?
You can't use that Dell external drive on another laptop that does not have a similar mating port.
That connector which I also have on my D400 is called a Dell D/Bay connector (see photo at http://support.dell.com/support/edocs/systems/latd400/smen/pinouts.htm) . The bottom half is just regular USB so you can connect anything with USB connector to it. I have done that with the small flash drives. The top half of the port has power pins.
my Dells:Optiplex 3020 - Windows 7 Pro 64-bitPrecision M6300 - Windows 10 Pro 64-bitPrecision M6300 - Linux Mint 17.3 Rosa / Ubuntu 12.04.5 dual-bootLatitude D620 - XP Pro SP3