How do I access this database files? (*.H##, *.I##, *.M## ...)

Question

I got software from a developer who move and can't be located, I just got the files but not the source code.

The thing is my client won't be using this software again but he wants to be able to access his data files from another application (the one I'm offering him).

I'm really lost, I've never seen any database (not sure if this is a database) with this kind of files.

Can some one point me in the right direction?

This are the files:

This are some of the files they copy as their database for backup.

So I'm almost sure this is the database, if I open them with a text editor, I can see some data but not in a secuencial way.

I feel kind of dumb asking, I already tried to look for *.H## *.P## *.B## extensions in Google with out any luck.

Hope some one can point me in the right direction.

Edit: I found connection in control panel, does this help any one?

Answer 1

https://fileinfo.com/extension/h16

According to this it is H&R block desktop application which produces these file extensions.