PANDA does not support importing DBF data files.
DBF is the format produced by long-lived database application dBase. It is a common file-format for data produced from legacy systems.
DBF files should be converted to CSV before being imported into PANDA.
If you are not a programmer, you can open a DBF file using LibreOffice. Once open simply choose Save As from the File menu and then select "Text CSV" as the file type. If prompted with advanced options (delimiter, etc.) you may leave them set to the defaults.
Note: Excel can not open DBF files.
If you are a programmer or are comfortable using the command line then the faster method is to use in2csv from the csvkit command line toolkit. This will read a DBF file and write a CSV file:
in2csv filename.dbf > filename.csv
Note: Whenever converting a file to import it into PANDA you should also upload the original as related file.