are you referring to 天灯节?
at 十分、平溪。
can take train from 瑞芳(same train station to transfer to 九份). Buy a one-day pass for 平溪(铁路)线at NT$54 and you can travel between 瑞芳 - 十分 - 平溪 - 菁桐。
but need to find out the dates.