My local host database has vanished (no replies)

Hi,

I updated MaraDB and as a rule of thumb, I normally back up my local host site database first. This time though, when I tried to do so by exporting the data base from phpmyadmin the database wasn't there. Because is a local host my phpmyadmins has no passport. Unfortunately I forgot my username and I tried with one word that allow me to get in but it could be one for another empty local host site I have.
How can I recover a forgotten username of my local web?
Hoe can I find out where the DB is located?
Apparently I still can access but I am worried than if I update anything in the future and I don't back it up, I may run into some big problems.

Thanks for your attention,