It appears that both .mpk and .aga files are used in ArcGIS geographic information system, but there is really no point to convert them or actually a way how to do this. If you are looking for something specific, please let us know in the discussion below.
Convert ArcGIS map package to ArcGIS ArcGlobe file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert mpk to aga on Windows
A group of GIS (geographic information system) applications
Convert from mpk file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.