While speaking to Milore Ienith in Raven Rock, she will task the Dragonborn with collecting five pieces of Netch Jelly.
Netch Jelly can be found within homes in Solstheim or other buildings, so it is best to check out the surrounding places first. Next, Netch Jelly is always found on the corpse of a Netch. So killing a Netch family will grant three Netch Jelly at the least.
Once 5 pieces of Netch Jelly are acquired, head back to Raven Rock and speak to Milore Ienth for the reward.
If the Dragonborn already has 5 netch jelly at hand and in their inventory, then Milore Ienth will respond with:
"My goodness, you're quite resourceful aren't you? This is all I can offer in return for this. I hope it's enough."
The quest will end right after the dialogue.