This was done during the switch from version 4 to version 5 (so more than 2 years ago).
Either you have partially mixed libraries from version 4/version 5 on your system or you are working on a design that was originally made in version 4.
If you have a mixed library setup then you might want to read this I had KiCad 4 installed previosly. Now i updated to v5. Now i have some problems with the library setup
If you are converting old version 4 projects to version 5 then this one might be of interest Converting KiCad version 4 projects to version 5 (Remap a project) (this focuses on the symbol side of things – footprints were not a focus as they are included inside the pcb files so a lot easier to handle without help)