https://www.quicken.com/support/how-and-when-use-intermediate-version-convert-older-versions-quicken
If your Quicken was before 2010 you should have several files making up the data. The main data file ends in .QDF. All Quicken versions prior to QW2010 store your data in a series of files all sharing the same filename but with different extensions like - .QDF .IDX, .QEL, .QPH and all 4 of those files were rolled into a single-file .QDF starting in 2010.