Merge 2 WhatsApp backups

Hello,

I have a problem, my old phone broke down suddenly, and I couldn't transfer my chats to my new one. I managed to recover a backup via the micro SD, but I activated WhatsApp before restoring it, and now I have a ton of new messages.

I uninstalled WhatsApp, and I have 2 backups (on my PC) with the same name msgstore.db.crypt.14

I would like to merge them to reinstall them in the phone's location, reinstall WhatsApp, and restore the new backup.

But I have no idea how to merge the 2 files... I've been searching for hours for free software or something, but my knowledge of computers, etc., is limited...

If someone can help me...

Thank you very much.