You probably don't need to do a 'conversion', after a single dose of Baquacil. Just chlorinate till it holds overnight, and you're good.

You may need to replace the cartridges, but you'd be better off with these anyhow
Unicel C-4607 Replacement Filter Cartridge (Easy Set Size A or C) @ Amazon @ Amazon
Unicel C-5315 Replacement Filter Cartridge for 15 Square Foot Intex B Filter @ Amazon
Get TWO -- these cartridges are MUCH higher quality than the OEM models. And CHECK first, to make sure you use the Intex "A", "B" or "C" cartridge.

Here's the recipe for Intex pool chemistry: http://www.poolforum.com/pf2/showthread.php?17055

Good luck!