Sorry, MCUXpresso IDE is very explicitly Cortex-M based systems only. If you need to target the old ARM7 or ARM9 based LPC2000 and LPC3000 parts, then you will need to stay with LPCXpresso IDE, or look at one of the various third party toolchains, such as Keil, IAR, Rowley etc.
There is also a brief overview of differences from LPCXpresso IDE, as well as some suggestions on porting existing projects, in the supplied MCUXpresso IDE v10.0.2 Installation Guide that you might want to take a look at (also downloadable from http://www.nxp.com/mcuxpresso/ide/documentation).
Regards,
MCUXpresso IDE Support