I'm replacing a Dell 290W PSU in an Inspiron Desktop.  I'm attaching a standard photo of it and a scan of the product label.  Also attached is a comparison of the 8-pin P connector (I assume this is the PCI-E) and the 6+2 PCI-E on the new unit.  The separate 2-pin lead, as you can see, is an opposite configuration of the 4th row on the 8-pin.
 
My question is, am I done?  Can I not use this PSU?  If so I'll need to return it  and seek another solution.  Any help you can give me would be appreciated.
 
The images are on Imagur, gallery Ff5Q3oK
 
 
 

I assume you are aware that Dell uses proprietary pin-outs on their MB and other connectors, or they used to anyway. There are converter cables available from various sources.
 
As @Epal2Apol said, seeing the photos would be helpful.
 
Strictly my personal thoughts, I would not do the PSU switch.  It is just not worth it in a Dell system.

If I go to https://imgur.com/Ff5Q3oK , it says that it can't find that page. I have no other idea how to find an imgur gallery.

As said, there are adapter kits available. It's up to you to find an adapter and determine if it is worth the price to upgrade your Dell system. The Dell forums used to be very helpful with this sort of thing, but I think it has declined somewhat. It's worth a try searching or asking for advice there. https://www.dell.com/comm...bd-p/Inspiron-desktops