It seems Poseidon for UML modeling software supports import of .xmi files (XML Metadata Interchange Format) and is able to use the data and save them in a ArgoUML model file (.zargo). Perhaps also possible in other UML modeling programs.
Convert XML Metadata Interchange Format to ArgoUML model file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert xmi to zargo on Windows
A program for modelling in UML language
Convert from xmi 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.