Don't know for sure but looking at the file extensions you'll need HjSplit to join them, freeware@
http://hjsplit.en.softonic.com/
Kinda selfexplaining how to do once you have the soft installed.
Ahwell, should you need instructions:
Both files + HjSplit in the same -(temp)-folder, run HjSplit and point to *.001 file, click on join.
Done.
Let us know for future ref is that's the case here.