MLD files refer to the multi-language dictionary files used by the AMLANGCONV command.
The path to the folder containing MLD files is in the system editor keys PowerPackPathsMldPath and Acad/MPathsMldPath(Configuration file settings gef@Paths@MldPath and gen@Paths@MldPath).
By default, the key points to C:\Users\Public\Public Documents\Autodesk\AutoCAD Mechanical 2023\Acadm\TRANSLATOR