Could anyone help with my Nougat updating problem?

[Android Central Question]

I have a Galaxy Note 5 N920A (unrooted) unlocked from ATT and used on another carrier, so I cannot use OTA updates. I'm going to flash it which I have done once before but my problem with this phone is that I have a lot of data on it that I believe is located in my root folder. apk applications that I don't know where the save data is. My question is where do I find the HOME_CSC file? I've seen on a lot of instructional articles about how to flash but they all mention this one file that I can't seem to find.
Thanks in advance.