How to extract sources (MNI) coordinates for time series

Requested array 15002*300000 array exceeds maximum array size preferences (32 gb) ERROR while extracting scout time series for a 30 min duration leg record of sleep

I am not sure what you are trying to do, but it seems you have extracted the time series from the entire cortex (15002 sources) at once, for a long recording of 30 min (300000 time samples). You may have defined a scout that covers the entire brain at once.

I tried creating scouts but but I am unable to figure out how to create an output with sources (voxels by voxel) with MNI coordinates like sLoREta

You mean extracting time series from specific regions of interests into a file?

Yes, after creating scouts, I wish to export the values into a .txt file for statistical analysis with baseline (Eyes closed data) in a matrix 128 (channel) * x time points. Will it be possible?

You first need to run the process 'Extract > Scout Time Series' after you have produced the source map and defined the scouts you wish to use. Once the array of scout time series is created, right-click over it in the Brainstorm data tree and select Export File. You will be able to select from multiple possible file formats from the pull-down menu.