How can i create a new emunand partition on the new SD ? did u mean recovery nand ?
just the way you set up the emuNAND partition on your old SD ... ...
hold L while you load the gateway exploit and you will see the GW menu, go to format emunand and your new SD will have an emunand partition on 4.X (whatever you sysNAND version is) .... (note: this will ofc format and hence delete all content on this SD card)
if you don't know that, then it makes me wonder, if you actually have an emuNAND set up on your current SD card?
gateway mode is NOT emuNAND, you have to actually set it up, it does not come automatically bundled with the launcher.dat