You will need dBase or some other program that can read dBase files in order to open them. Otherwise you will need to get another program to open them, but they would ten be opened in a windows environment and in the program.
You cannot open the files directly in DOS. You need to have dBase and run it from DOS. If you have dBase, and you had it in a folder on your C: drive called Dbase, on the DOS command line, or going through Start and Run, you would type:
C:\Dbase\DBASE.EXE
Once dBase is running, assuming the dBase file is in the same folder, on dBase's command line type USE and the name of the file. So if the file was called names.dbf the command in dBase would be:
USE names