How to get the inverse martrix?

Suppose there are 126 scalp electrodes now, and I want to map them to 2000 sources. How can I get the mapping matrix from 126 to 2000 in BS and derive it? In theory, if I know the mapping matrix and derive it, then I can analyze the source signal anywhere, such as in python. I tried to calculate the source in BS and export the source signal, but I didn't find the source signal data in the exported MATLAB variable region, only some matrices, and I was thinking, is there one of them I want?

I performed a sLORETA transformation of the scalp EEG signal (using a noiseless model) and then imported the source signal into matlab (right click->File->Export to Matlab) and I found a type double matrix called 'ImagingKernel' with size 1004 × 126 (1004 represents the number of sources and 126 represents the number of scalp electrodes).Is this the mapping matrix that I need?

Please refer to the introduction tutorials: