Since Joe Harris’ arrival in Brooklyn, Nets coach Kenny Atkinson has set about building his battered confidence, convincing him he could be an elite shooter. Now that’s the exact goal the off guard has set for himself. Harris — essentially plucked off the scrap heap in July 2016 — became the Nets’ best 3-point marksman last season. But this season, he wants to become one of the best in the NBA, setting the 40 percent barrier as a personal benchmark. “That’s just a personal goal of mine,” Harris, 26, said at training camp at the Naval Academy. “I hovered around 38 and 39 percent last year. If you look at all the top shooters in the NBA, guys that might be specialists — like how I see myself as a good shooter and specialist — they’re always 40 percent and above. So that’s a personal goal for me to get into that elite 3-point shooting percentage.” Part of the trick was convincing Harris it was possible. He had spent his first two seasons bouncing between Cleveland and the Cavaliers’ developmental league team in Canton, Ohio. Harris eventually suffered a foot injury, got dealt to the Magic and promptly was waived — but during his time in the Cleveland organization, he had made an impression on Cavaliers assistant Bret Brielmaier and director of basketball operations Trajan Langdon.