@cskoog 

something like this, and christopher had got my intention.

here in Mathematica code, Join 10 .txt files.

Mathematica's .nb files can be import by NotebookRead[] or Get

filesImported=Import/@files;

fileToExport=StringJoin@filesImported

Export

@Christopher2222 

You've got my intention.

@cskoog 

@Christopher2222

Yes, just like what Chritopher said,

When I export 10 .mw files to .html, and each .mw file contain little content, so it's boring to open each .mw files too copy the content too many times.