Normally 3 bits, but when correct all should be joined/bolted tight together and not seperate.
There is the "tube" part of the tappet then the pad that the cam bears against, then underneath the pad is a locknut, ie the tube part is threaded and the pad wound in or out as needed, then the locknut locks off the adjustment, assuming it's that sort, some are simply tube part and shim, much better imo.
tabetha