you will need a USB hub, preferably powered and a Thunderbolt to VGA (or DVI) adapter
Then you can put all the USB devices into the hub and the hub into 1 USB port.
The external monitor into the Thunderbolt port, using the adapter.
That leaves the Firewire port free and, if you are using wireless, the Ethernet port too.
I have 2 External HDD (1TB - Western Digital My Book and My Passport USB 3.0 ).
can I Plug these 3 External HDD and one external Monitor ( Or TV ) to MacBook Pro 13'' ( MD102 )
MD102 have 2 USB ports +
1 Thunderbolt port
Gigabit Ethernet +
1 FireWire port