Welcome to Android Central! SMS messages are stored in an SQLite database in a protected directory. You won't be able to access them (unless you root the phone).
I just did a FR on DH's phone and can't find where to install/import the cvs file that contains his text messages. I have a copy on the SD card and on my computer. When I click on "my files" and navigate to the SD card, I can seethe csv file...it's named "contacts" but I created it in the default message app by choosing "save messages". Hope someone can tell me where to install this csv file so I can get his text messages back