The largest bulk carriers manage about 400,000 DWT.
So, about 1000 trips of the largest around... ignoring the logistical and ecological challenges of procuring that much material and using it to raise the island in a durable way.
I hope the math for how much it costs isn’t so low as to be sad to fix this problem in the wrong way.
Why not give the cost of that operation to every Tuvaluan, along with a promise that they and their family can emigrate to a country of their choosing?
But more importantly than the amount you need to raise the islands: 26 sq km * 1 meter probably doesn't raise the islands anywhere close to 1 meter, because of:
* Early losses from erosion and compaction
* The angle of repose around the islands (you can't just build the island straight up 1 meter).