4 Nephi 1:41

And they did still continue to build up churches unto themselves, and adorn them with all manner of precious things. And thus did two hundred and fifty years pass away, and also two hundred and sixty years.

They kept building churches for themselves. They decorated them with all kinds of valuable things. Two hundred and fifty years passed. Then 260 years passed.

They kept building their own churches, decorating them with expensive treasures. Years 250 and 260 came and went.