How do I reinstall backup files on ATT S4 ACTIVE?

[AC Question]

I purchased a Galaxy S4 active that was not blacklisted. I connected it to my computer to check files, so that I can unlock the phone to use with Family mobile. files were missing. I installed my family mobile SIM card into the S4 and received the unlock/ dismiss. I pressed the code block and got to the dial pad tried the *#0011# got nothing tried for IMEI numbers got them. But that's it. How or where can I find what I need to use this phone? I could use a lot of help Thanks