Reshape the exported PLV file to N*N matrix

Hi all,
I exported the PLV file from brainstorm to matlab. This exported file is structure type. Actual calculated PLV value is included in ‘TF’ field (in my case 6248118 double)(62481 is number of PLV, 8 is freq bin).
I want the NN (in my case 350350) matrix file format as like displayed in brainstorm.
I would be happy if you could give me some advice how to reshape exported file.

Thank you in advance,