Shutdown Emby Server. Do not do any part of this with Emby Server running. Your library info will be stored in a path similar to this on Windows. Change the bolded text to be the username Emby runs under. C:\Users\Administrator\AppData\Roaming\Emby-Server\programdata\root\default. If you need help locating this path on another platform ask. Your Data Path is shown in your server log or as part of the Paths shown on dashboard.  In 4.7 that will be the three dot menu next to power Butt