To use the 2D LED module you would need the parallel adapters (to maintain 2 x cell voltage).
The 2D LED module
will with 6 AAs in series.
A common/lowish cost LED upgrade with 2 x series 3AA/D is to use the Terralux 6EX LED drop-in, which (unlike the Mag 2D LED) will run off 6 AAs, and has about twice the output of the 2D Mag LED.
If you want to 'upgrade' to a 5 cell Xenon/Krypton incan. bulb (as the OP did), then you would need the series adapters (for 6 times cell voltage). This is slightly overdriving the cell, (and so shortening its life) but this does mean a whiter and brighter output.
This also opens up the potential for much bigger and better incan. upgrades (ROP, 5761 etc), although for these you need a better adapter, and other upgrades.