Connecting the display pins directly to Arduino I/O pins is not a good practice. For testing purpose only one 330 Ohm resistor (R2) is added between ground rail (0V) and the common cathode pins (3 & 8 ...

To get a LED lighting we should connect its ground pin to the circuit ... the sockets four 7-segments LED common cathode LCD display devices, we should connect the pin 33 of the board (the common pin) ...