It is certainly possible to export PlanMaker spreadsheets to old Navy DIF format, but it does not work that way for templates (.pmv files) directly. What you can do though, is to prepare a new sheet based on the template and export that, but this does not make sense for DIF files that do not feature any formatting.
In the end pmv to dif conversion is a bit odd and perhaps it might have been a typo originaly for some other file type(s).
Updated: November 3, 2023