Can we use ULN2003A to power up another module
The ULN2003A is a 7 channel low-side driver that is rated for 500mA per channel, but drops ~1V at 400mA.

If your module will work with ~1V less than your supply voltage and its ground pin being raised by 1V isn't a problem then it may work (though the ~0.4 W power loss in the ULN2003A could make it very hot). 

However if another device has to communicate with the module then the raised ground potential probably will be a problem, so it would be better to use the ULN2003A to switch a high-side power transistor, like this:-







simulate this circuit &ndash; Schematic created using CircuitLab

The high-side switching device can either be a PNP bipolar transistor (as shown here) or a P-channel MOSFET designed for 'logic level' Gate drive (eg. IRLML5203). Either type should be rated for several Amps to ensure low voltage drop at 400mA.