Your answer will be 10m.
We can picture this question as a right-angled triangle, where the pole is one leg, and the distance from the pole to the pigeon on the ground is another leg. Using this, the hypotenuse would be the distance that the pigeon would travel to get from the ground to the top of the pole, presuming it flies in a straight line, and so we can use Pythagoras’ Theorem to find the length of the hypotenuse.
a² + b² = c²
(6)² + (8)² = c²
36 + 64 = c²
100 = c²
10 = c
I hope this helps! Let me know if you have any questions :)