DII to DAT File Converter - Version 1.0 DII to Dat File Converter is a free tool to convert DII files to DAT files. It reads the starting number and the ending number from a DII file. Once read it is written to a DAT file in the format of "starting file","ending file". To use the program simply browse to the DII file and click on "Continue" the DAT file will be created with the same name and in the same folder as the DII file.