Tab Delineated format (.tdl) is essentially a specially formatted format (similar to CSV) and widely supported in most spreadsheet programs, including MS Excel and some open programs like LibreOffice / OpenOffice.org Calc.
Simply open / import your files to Excel and select the proper separator to properly parse the data. After that just save the data to one of the Excel formats like .xlsx files, which essentially achieves tdl to xlsx conversion for you.