the part you are missing is almost always attached to the cabinet or case - and if you only got the machine, that is why. It makes it real easy to take the machine in and out of the cabinet wired this way, most of my "dashboard" machines are like this. There is usually one screw holding the block in place, so it's not much to remove and take with, but often the machine is taken by someone without a clue - and they don't realize they should be removing that also.
Sort of like all the machines you see for sale that are missing foot pedals - people grab granny's machine but don't think to look for the power cord.
Rodney and Joe both posted what you need.