I paid about AU$300 for my prebuilt system which I got from here:
MODERTOR : DELETE LINK NO PUB FOR YOUR RESELLER
I opened it up, and it has a lead going from inside the console to the outside where the SD card is situated. When I plugged in my 2TB portable drive into the one of the bottom USB ports (it has 4) it copied over a folder called 'recalbox' with bios files, a roms directory with all the different consoles, and a bunch of other directories, but none of the roms from the SD card. I put all my roms into their respective directories on the portable drive, went into the menu setting and changed the data storage to external and rebooted. It still used all the roms located on the SD card, and I could see when it was booting up, there was no activity on the portable drive, so it was not being used. I have to presume that since there is an option to choose from the internal or external 'drive' then it must support some sort of external data storage. I had bought a Pandora system on the understanding that I would be able to import SNES games, only to find out that my system was not compatible with that, which is why this console was recommended to me. I am sure if you are able to help me, you may require some more information from me regarding what version of recalbox I am using or other information. I hope I hear again from you with some advice, as you are the first person who has reached out to me offering me any kind of help at all. To assist you, I have attached a few screen shots of what was copied to my external portable drive. Most of the directories are pretty empty, except for the BIOS and SYSTEM directories. I have attached snapshots of these for you to look at. Where you see "Retro Pi(E:)" that is referring to my external portable drive. Again thank you for replying to me.