I have a refurbished Dell Optiplex 755 (USFF).  I wanted to upgrade it to wireless, so I downloaded a manual which said it was very simple--buy a PCI wireless adapter, install it into a PCI slot,and all would be good. I purchased a TP-Link adapter.  However, when I open computer case there is no slot as far as I can see. I am not a computer whiz, so maybe it is there but I cannot see it.  This computer is I think the smallest in the 755 series. So, despite the manual instructions, does this mean I cannot convert to wireless?The Dell SFF computers do not have PCI slots. No room. But they make up for it with lots of USB slots  Two in from and five in back. A small USB adapte4re qwill work fine. I have used both the Ethernet and a wirelesses adapter on tghe Dell 7556 and the performance is good either way.

Images and prices of USB  wireless adapters.
This is what you want.

If you get a big one, they TEND to want to COME out of the USB slot. If that happpens, use a bit of string to TIE it up.
Thank you, thank you, thank you...I will get one TOMORROW and install.Thanks again!!