To get inside the Rocket Warehouse, you must have two passwords.
If you go to Mt. Ember on One Island, you will find a cave to the right side which is garded by two Team Rocket Members. Go to them and you will overhear their converstion. One of the members will say the first password to the Warehouse.
Note: Make sure to go in the cave an write down the brail alphabet that is inside. You will need it to get the other password.
To get the other password, you have to find the Sapphire on Six Island. When you try to take it, a guy will come out of nowhere, take your Sappire, and run away! Talk about rude! But, he does give you the other password to the Warehouse, where he has taken it.
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In Pokémon FireRed, you can find Nest Balls in Team Rocket's Hideout in Silph Co. and in Team Rocket's Warehouse on Five Island and you will also be given a Nest Ball from the Lady in the Water Path in which measures the sizes of Heracross trainers have captured and if the Heracross breaks a record then she will give you a Nest Ball.
Get team rocket to go out of five island hideout (using the blue gem) and talk to Lorelei.
In the Pokemon FireRed and LeafGreen games, some of the Team Rocket hideouts in the Sevii Islands are protected by passwords. All passwords are obtainable in-game; to get the Five Island's password, the player must continue to Six Island, whereupon the player will receive the password as part of the plot. The player can then go back to Five Island to complete the mission there.
Its an area south of five island.
Trade from colloseum or island Five