No, modern Dell proprietary mobo has long got rid of usb 2.0 9 pin header. Use a usb dongle might be easier if your pc has no M.2 WiFi card and its antenna.  I am a bit surprised as the basic config should include an M.2 WLAN card.  Motherboard layout has an M.2 WLAN slot. Re: 2.5 sled you can use Dell YHNFX 2.5" drive caddy. That caddy is also used in six other Dell PC models. but it is expensive, $19-25 each.  It looks similar to another Dell 2.5 caddy X9FV3, which is less expensive, $7 each.  The only difference seems to be metal grounding tab present in the first and absent in the second. [IMAGE] YHNFX [IMAGE] X9FV3  
Two questions regarding my new Vostro 5890: - I can't find a USB 2.0 9-pin header on the motherboard, but is it possible I've missed it? I intended on installing my PCIe Wi-fi card in the system, but apparently it won't function without a USB connection. - Can anyone specify a part number for the drive sled for the two 2.5" hard drive slots at the top of the case? (I've ordered one on eBay that looks like it might work, but it hasn't arrived yet. All I have to go on is the thumbnail illustration on the case cover; there's nothing in the manual on it though there are power cables and open SATA slots.) Thanks!
Vostro 5890 USB header, drive sled