What is the important difference between 1.3.8 and 1.4.2?
What are the reasons why you must use 1.4.2?
Copy the playlist of 1.3.8 to 1.4.2 import, the names are all numeric serial numbers, 00..1~000..9, how to restore the name?
You are aware of the change log (http://www.foobar2000.org/changelog)? I don't know how the differences between the two versions could be reduced into single entity. You should also read version 1.4 release notes (https://wiki.hydrogenaud.io/index.php?title=Foobar2000:Version_1.4_Release_Notes).
Internal playlist format changed in v1.4 and it isn't backwards compatible with the old one. If you upgraded the old playlists were left intact in playlists-v1.3 directory.