Go to this link, which gets your the HP QuickSpecs document for the Z240 SFF, HERE
http://h20195.www2.hp.com/v2/GetPDF.aspx/c04762288.pdf
Go to page 2 and look at number 5. That workstation already has a built-in serial port for you.
Another thing.... those SFF (Small Form Factor) workstations all cannot accept full height cards. Some cards are half height and come with both a full height and a half height metal backplane adaper which lets you use them with a greater range of workstations. But the card itself needs to be half height for a SFF workstation. That card you show seems to be able to be reduced to a half height card if you take off the top cable and swap in a half height backplane adapter that presumably would be included in the box. They might even include two half height backplane adapters so you could use that second serial port side by side with the first one.
But, you may only need one, in which case one is already built in. And, here is some important added news: From that QuickSpec document comes this:
Serial 1 rear port
2nd Serial Yes- requires optional Serial Port Adapter Kit
That adapter, listed in there as PA716A, is exactly the same one we have been using in HP workstations since at least the xw generation, and you can find those still new from HP or used off eBay. I have posted here on that and their serial numbers. There is a header on the motherboard you plug into, and route the flat cable over to the backplane. Those kits new include both full and half height backplane metal plate adapers. The HP motherboard connector and the flat cable and the PCB you'll see if you look this up all are proprietary, so be sure you're getting what you need if you don't buy direct from HP.
So, this would be a way for you to add a second serial port to the first one that is already built in, without having to buy the card you linked to. See picture above the QuickSpecs page......
