First, go to the shipyard in Slateport. Talk to the man that you first come across, who seems to be staring at a piece of paper. He tells you that Captain Stern is at the museum.
Go to the museum at the east of town, then talk to Captain Stern on the second floor. He'll take the goods and arrange to leave. Before he can move, 2 members of Team Aqua will come in and try to steal the goods. Battle them, and when you defeat them both, the Aqua leader will come, give you a brief warning, and leave.
Edit: punctuation, grammar, and clarity improved
You go to slateport and you deliver the Devon goods to captain stern.
You can either go to the next route or get the exp.share from the president.
Capt. Stern is not in Pokemon Leaf Green. He is only in Pokemon Ruby, Saphire or Emerald.
You deliver Devon's Goods to Captain Stern who is in Slateport City's museum.
In the slateport city boat dock place
You go to slateport and you deliver the Devon goods to captain stern.
You can either go to the next route or get the exp.share from the president.
Capt. Stern is not in Pokemon Leaf Green. He is only in Pokemon Ruby, Saphire or Emerald.
You deliver Devon's Goods to Captain Stern who is in Slateport City's museum.
In the slateport city boat dock place
While in Lilycove City, you can find Captain Stern in that museum place where Team Magma/Aqua are standing by. I forgot how to get rid of them, but once you do, you can find Captain Stern in that museum place I mentioned.
In the Slateport museum.
It's the Seafloor Cavern... An underwater cave where the legendary pokemon, Kyogre is sleeping.
Once you get the scanner, go to slateport and find captain stern, he will trade you a hold item for it.
a guy will ask u if u can deliver Devon goods to captain stern..captain stern is found in the museum of slateport(specifically 2nd floor).
the presedent of the devin corpration gives a pokenav to us when we save the Devon guy from team aqua/magma but he also tells us to delever a letter to steven and the Devon goods to stern in slateport
Captain Stern is on the top floor of the museum in Slateport City.