Pardon if this seems too old to resurrect, but those are almost definitely #6-32 UNC screws, i.e. UTS #6 (0.1380 inches) and 32 TPI (Threads Per Inch). In order to tap screw holes this should be all you need. In this case the screws have a T8 head fashioned to provide the hard drive with a set of studs when installed to hold it in place. In addition to #6-32, Metric M3 Fine pitch screw is often used for mounting SSDs, optical media drives and various other things. The typical length of case/hard drive screws is around 7/16”, but there is some variation for differing mounting brackets and shock reduction designs.