You can only get to Islands 8 and 9 in Pokémon FireRed through the use of cheating devices or through events which will give out the tickets which are needed to access the Islands however the events are no longer available.
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cinnabar islands
You can't because there is no Pokemon Center in Seafoam Ilands.
you can go on the seivii islands 4 to 7
You need the rainbow badge which you get a celadon city Hm cut is needed.
He will be at his house, if you didn't go to the islands yet he will be in the cinnibar island Pokemon center.