Converting fmri data to association matrix
You can get raw FMRI data from https://openfmri.org/ on that website you'll also download your conditions files for the experimental design (you'll need this in creating your matrix). This is a link to an experiment(it's data) with "healthy" participants and participants diagnosed with schizophrenia: https://openfmri.org/dataset/ds000115

Raw image files from a scanner will be in .dcm format. You can use http://www.mccauslandcenter.sc.edu/mricro/mricron/dcm2nii.html to convert the multiple ".dcm" images of a scan into a 3 single 4D images for anatomicals, also known as T1 images. That converter will also convert the BOLD images into a single 4D image. 

After conversion, the images you will want and need to load into whichever fmri data analysis software you're using will be in ".nii.gz". 

Your question suggest that you don't need data analysis software but if you do,  I'm only familiar with FSL, you can find information on FSL from here http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/

Hope this helps.