IFO files from DVDs do not contain any multimedia data, so it is not possible to convert ifo to wav or any other audio/video format for that matter. You would need to convert the actual video, represented by a .vob file.
Convert DVD movie information file format to WAVe PCM Sound, standard Windows sound format.
We found 2 software records in the database related to .ifo to .wav file format conversion.
Microsoft Windows software - convert ifo to wav on Windows
A multimedia converting tool for Windows
Convert from ifo file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned ifo to wav. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert ifo to wav on OS X
A video ripping tool for Mac