need help printing acme nut block

i downloaded the iges library found the file for the nut block then used a website to convert it to stl, i load it into octoprint and it shows up in the slicer and looks good except when i print its missing the hole for the 8mm rod to go into..... the 2 bolt holes are there, its just the 8mm rod hole is filled in for some strange reason

how do i fix that, and also will it have the threads for the rod? in the slicer it looks like a smooth hole which would make it useless???