Okay, I already have the blood elder scroll. I left the soul realm but i have no clue where to go to find the dragon elder scroll? I've been stuck for the past 2 hours trying to find and objectives on how to find it. I tried taking to the Moth Preist but he keeps saying im his master. I talked to Lord Harkon, nope he doesn't say anything.. When do I go to find this last elder scroll???

The dragon scroll is the scroll from the main skyrim quest. If you have it, it should be in your inventory. If you sold it to the orc in the library at the college, you have to buy it back. Otherwise you have to go to Septimus Signus Outpost and get the quest to blackreach for it.