how to merge dbf files

Never found a merge, but there is an APPEND command. Documented at
https://msdn.microsoft.com/en-us/library/aa977271%28v=vs.71%29.aspx

Good afternoon,

If the columns (fields) have the same name in each DBF file (table), the process is fairly simple. First, decide if you want to use one of the three tables to hold the final results, or keep the three tables as they are for historical value.
Also read more DBF Viewer Tool for solution: http://www.dbf.viewertool.com/
I'll give you the second option, just because it's a better choice. I don't know the names of your tables, so I'll just use File1, File2, File3 and Final as the names and you can substitute the real names in each case. All of the following commands should be typed into the command window. Each command will be executed when you press the enter key (after typing each line). FoxPro commands will be in upper case and must be exact, the table names will be in mixed case and need to be changed to match your specific files (the extension (.DBF) is optional).

USE File1
COPY TO Final
USE Final
APPEND FROM File1
APPEND FROM File2
APPEND FROM File3
USE

The final command will close your <Final> table. If you want to do something with it right away, don't issue the final USE command. If you want to look at the results, type BROWSE before the file is closed. Press ESC to close the BROWSE window; remember to issue the USE command after looking at the file so it will be properly closed.