As a non-expert, I recommend you run the FreePBX Distro. Install ver. 13 and use Backup and Restore to move your current config or install ver. 14 and use this to migrate your settings:
https://wiki.freepbx.org/display/PPS/Elastix+and+PBXinaFlash+to+FreePBX+Distro+Conversion+Tool
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Upgrading from FreePBX 13 to 14 on centos 6.9
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