Both the .dgr and .dgpd files are documents prepared and saved in DeltaGraph statistical visualization software. No specifics regarding this conversion could be found on internet, but it is likely these files can be only handled using DeltaGraph. That is, if this conversion is actually useful at all.
Convert DeltaGraph document file to DeltaGraph Document file.
We have found one software suitable in our database for this conversion.
Apple macOS / Mac OS X software - convert dgr to dgpd on OS X
Software for making perfect charts and graphs
Convert from dgr 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.