Which race is stronger blood elves high elves or night elves

None.
None of the three races is necessarily stronger or weaker than another. Typically, it is seen as Night Elves having more power over nature, High Elves having more power over the Light, and Blood Elves having more power over Arcane and Fire, but even this is a generalization. All three races are powerful, but their power cannot be compared to one another. Also, though the Blood Elves seem to be more willing to use their magic in near-reckless ways, the Night Elves and High Elves usually choose to refrain from destructive magic. There isn't any true "stronger" race among the Blood Elves, High Elves, and Night Elves, there are just differences among the three races, just as with all the races in the Warcraft storyline.