a bar magnet has no marking to indicate poles. how will you find its poles without using a magnet
the power of magnet is situated on the poles you can prove this as put some pins in a container put a magnet in it shake well the container after a while you can take out the magnet and you can see that all the pins are attracted to the both end of the magnet this determines that power of magnet is stored in poles and the place where the most pins areattracte can be said as it's poles
Afreely suspended bar magnet always comes to rest in the NorthSouth direction. The north facing end of the magnet is its north pole, and the south facing end is its south pole (as shown in the given figure).
Hence, the unknown poles of a bar magnet can be marked by suspending it freely by a string.