The video tutorial that you will see below guides you on how to get the dawnbreaker sword. Follow it step by step and you will find the location of the dawnbreaker sword. You need to follow each step, from getting the statue to entering a cave and many more things.
This here roughly explains how to acquire this task but for more details take a look at the video guide. Meridia will ask you to become her champion and restore her influence over Skyrim by restoring her temple, which has been hijacked by a necromancer. She commands you to first find her beacon that is seemingly spawned into different locations for different people. Upon placing the beacon in the players inventory, Meridia speaks to the player, commanding you to take the stone to her shrine, which is located west of of Solitude, almost directly south of Wolfskull Cave. Once there, Meridia will tell the player that there is a powerful necromancer defiling her temple, which the player must navigate through and kill.