I bought a new my new MacBook Pro. I found that the number of charge cycles is 2 cycles, Is this normal for a new MacBook Pro or it is used ?
To me this value looks completely normal. Apple needs to use the battery for quality testing.
That represents the results of testing during build and Quality Testing.
A used MacBook will have well over 2 battery cycles.
Cycle count on a battery can't tell you if your Mac was new or used. Why?
In both of the above scenarios, you would have a low cycle count, but actually have used equipment.
Additionally, a 2017 MacBook Pro is the previous years model (as of this answer), so it's entirely possible you have something called NOS or New Old Stock. Battery charge levels will drop, so to make the unboxing experience a positive one, retailers will often times remove the device to charge it up and re-shrink wrap it.
Also, looking up the serial number is not a definitive way to see if the unit is used or not. The SN# database is updated upon registration of the device. If the Mac is never registered nor signed in with an AppleID, it won't show in a SN# lookup.
At best, these are indicators, but they are not definitive.
It's important to note that you can have a new product actually contain components that came from an previously opened/used item. In this answer I reference an FTC opinion on a Sony case involving the recommissioning of previously owned products as new (spoiler: it's legal).
So, how can you tell if the Mac you are buying is new or used?
Buy from a reputable source. Scams do happen, but there is a level of protection when buying from reputable sources. Buying directly from Apple or a retailer you trust goes a long way in ensuring you get what was advertised.
Physically inspect the item. Does it have that "new tech unboxing experience?" Does the plastic protective film look factory applied? Do the cables and boxes look properly sealed, coiled, and secured?
Boot the machine. Do you get that new user "Welcome" experience or does it look like an account was created?
When in doubt, return it! You paid good money for a laptop. If you feel that it's not what you are expecting and you have lingering doubts - return it for exchange or refund.
Two charge cycles on a new MacBook that's technically 1 year old is perfectly fine. Unless you have something else that's jumping out at you that this is a used device; in all likelihood, your device is brand new.