How to get the gain in db against frequency curve for this parallel LC circuit in pspice?
Not a PSpice user so I can't comment there, but here's how it's done in LTSpice. I assumed you wanted a voltage source instead of a current source as you've drawn it, but your post isn't very clear. The following instructions will also work for a current source.

First, make the schematic, setting the voltage on the source to "AC 1":



Then, create the simulation by going to Simulation -> Edit Simulation Command. I did a sweep from 1 Hz to 1 MHz in 100 pts/decade.



Now you can click the output node to get the Bode plot:



Hope this helps.

Side note: as your circuit is purely reactive, the gain is very large at resonance. This is voltage gain only - this is a passive network and cannot exhibit any power gain. To demonstrate this, try assigning an impedance to the source and loading up the output.