i want modem file from G920p 5.1.1 version

Hello pls am new here and wanted to know if there was a way to get my g920p network working. I updated it to marshmallow and the network stopped working. I heard extractingt the modem file from the 5.1.1 and flashing it. will make it work. But haven't tried it yet. And also I want the link for the modem.bin from the version 5.1.1.thanks