That function is part of an older hardware driver called traditional DAQ. It can be downloaded from here. First though, you need to check if your DAQ board is supported with traditional DAQ, the newer DAQmx, or both. You can find that information here.
I've been trying to use AI.LLB, in order to open an old project. However, I have the Labview 7.1 and 8, and the only DAQ I can find/download/install is the DAQ-mx 830, 750, 693 which don't have AI.LLB.
I'm also trying to use AI Read One Scan.vi Isn't it supposed to be in C:\Programme\National Instruments\LabVIEW x\vi.lib\DAQ\AI.LLB ?
I don't know where you tried to find the traditional DAQ drivers but they are all listed here and the latest is 7.4.4. The 6.9.3 version is not DAQmx and is a pretty old version of traditional DAQ but if you installed that, the library should be there.
I have a similar problem, except that I'm updating old traditional DAQ code to run in DAQmx. What would the appropriate replacement VIs be in DAQmx for reading and writing one sample? Also, do I need to setup tasks for each channel in MAX to do so or can I have one task handle all channels?