That would depend on the drivers which are supplied. If there's an API library, you should be able to use it with most languages without problems.
If its the one i thinnk it is then best to use c according to this from NI The USB-6501 comes with NI-DAQmx Base driver software, a multiplatform open-source driver for Windows, Mac OS X, and Linux that includes the NI-DAQmx programming interface. With the driver software, users can quickly develop customized data-acquisition applications using the NI LabVIEW graphical programming environment or C-based development environments However, with a bit of extra work you could alost certainly use it with vb using COM interop.
For clearing your basics about how computer think you must go with C. But C++ is far better than C, its library has lot of functions inbuilt making it easier, if you are interested in data structures. Better to Learn C++ than C.