I'm trying to put together an old Ikea table as an extra desk on which to work due to Covid related work from home. It is missing one of the four sets of threaded rods, washer and bolts that it needs. Plus it is missing the piece that sits inside the table leg in which the threaded rod secures itself. I'm looking for the name of this piece, and if possible, how to get a replacement for the whole set. I got a washer, nut and threaded rod at the hardware store, but don't really know how to go about getting the other piece as I can't even search for it without a name. See attached pics.