Multiecuscan

I read http://www.multiecuscan.net/SupportedVehiclesList.aspx and I see theres is an Adapter cable 3, and a 3-pin adapter cable...
I need (I think) the 3-pin adapter cable, to reset a Fiat 500 1.2 8V service indicator...

But in http://www.multiecuscan.net/SupportedVehiclesList.aspx there is only a diagram for adapter cable 3, and no word about 3-pin adapter cable...
What is the difference?

The 3-pin cable is an adaptor for early vehicles that did not have the standard 16-pin OBD-II / EOBD type connector - instead they had a Fiat-group specific port with 3 pins in it.

On a Fiat 500 you won't need a 3-pin adaptor.
You will need an Adaptor 3 cable though, as this redirects the CAN lines to different pins in the diagnostic port, to enable communication with some systems. The adaptor 3 cable is a 16-pin connector at both ends, it just moves the signal to different pins within those 16.