Convert the results

Hi. Yes, you are right. I found this problem yesterday. I am trying to export source results to spm12, and writing code to flip results directly.
In this process, I have two questions. One is the source results have 15002 points when i export it to matlab, is there a mask or some other way to tell me which part of the brain this 15002 corresponds to. The other one is that i export results to the file of '.nii', and i wrote code to flip the first dimension of data, but i cannot import flipped data to brainstorm, how can i import flipped data into brainstorm, it awlays report an error:" number of source is different from the number of vertices". How can i import flipped data successfully.
Looking forward to your reply. Thank you very much.