VCC is the voltage that it needs for its own internal operation 5v; L293D will not use this voltage for driving the motor. For driving the motors it has a separate provision to provide motor supply VSS (V supply). L293d will use this to drive the motor. It means if you want to operate a motor at 9V then you need to provide a Supply of 9V across VSS Motor supply.
The maximum voltage for VSS motor supply is 36V. It can supply a max current of 600mA per channel.Since it can drive motors Up to 36v hence you can drive pretty big motors with this l293d.
VCC pin 16 is the voltage for its own internal Operation. The maximum voltage ranges from 5v and upto 36v.
TIP: Don’t Exceed the Vmax Voltage of 36 volts or it will cause damage