Hi. 
I keen on working on PCI-6221 using DAQmx. 
you can find everything about installing the card and creating tasks in Measurement&Automation in pdf file DAQ Quick Start Guide - you should have this document if you had installed NI-DAQ. 
how to create tasks dynamically you can find in examples - and how Neville sad: "It is difficult to find one-to-one correspondence for all the various combinations of DAQ processes, AI, AO, DIO, Counters/Timers, Triggering etc etc. without knowing any specifics about your application. It will take a while to convert to DAQmx, but it is worth it." 
progor