Well, you have two issues to deal with....
First you have purchased the older neoflash mk1 linker set (which is no longer supported here). Thefore, you won't be able to run some of the newer commercial roms....
The most current neoflash product is the mk3. If you want one that comes bundled with a 512 Mb flashcart, this is the appropriate link:
http://www.divineo.com/cgi-bin/div-us/dd-nds-neo1However, the software is still being developed, so there are still various bugs, so don't expect 100% compatibility...
Your second problem is that you have a newer firmware version that is not compatible with any magic key (mk1/mk2/mk3). This means you need to buy a separate device to add compatibility (called PassMe2). The idea is to replace your incompatible firmware with a hacked, older version that IS compatible with mk1/mk2/mk3 (through an application called Flashme). PassMe2 can be used to install the Flashme firmware on your ds.
You can purchase a PassMe2 device here, or buy equivalent commercial versions : SuperPass2, Passkey2, EZPass2.
http://www.dspassme.com/You should read the mk2/mk3 guide for more detailed information here:
http://www.neoflash.com/forum/index.php/topic,1529.0.htmlSpecifically, read Requirement #2 about PassMe2, and understand that part well before even purchasing a PassMe2 device, if you decide to go that route.
BruceG