If you create an MDA the filename normally contains the version number. To get the latest one you have to open the modeller, retrieve the latest model and build the MDA.
If the project is not a Team server project, there will be no version control and no version number appended to the mda files :(
The easiest way to identify the latest version is by the date/timestamp on the windows file, or failing that, the latest one is normally the biggest one - projects always seem to get larger over time !