Knock sensor location

Is there any specific location where knock sensor should be mounted?

No per say, but you have the best location, which is somewhere in the upper middle section of he engine, and then you have like second options around the area, and then some less effective places,

So in your case you are trying to add a knock sensor so your engine may not have one as all engines with knock sensors come with a threaded mounting point that is the best location for it,

Use a location in the upper middle of the engine if possible if not locate a mounting point as close to that area as possible, if none available you could use the side covers or even the head but those are not the best places, just check what spots you have and work with them

Thanks

As Gurur has said, the middle/upper cylinder block is ideal but often you're compromised on where you can find a spare bolt hole on the block. In my own experience almost anywhere on the block will work well though.