Newb Needs Help (stuck trying to upgrade baseband on 3g)

Hello, ok right I have a 3g.

Currently running 4.2.1 with baseband 05.15.04.

I jailbreaked phone first with Redsn0w. Once Cydia installed I installed Ultrasn0w but the phone is obviously not unlocked. Later I learnt that I have to upgrade to ipad baseband. (I understand the risks and I am happy to install the new baseband). Problem is Im stuck on how I install the ipad baseband?

If I plug in the iphone and run Redsn0w there is no option to install the ipad baseband (which I have seen on other tutorials). I start redsn0w, point it to the 4.2.1 file (it checks it as usual) as then I am presented with several options, install cydia etc etc but no upgrade ipad baseband?

Clearly I am missing something probably very obvious. Can some one point me in thr right direction?

Thanks

Only specific versions of PwnageTool and redsn0w have the iPad baseband option. I believe you will want to use redsn0w 0.9.6b5, though there are a few newer versions that will also install it, I don't know any of their versions off-hand.