Migration from PL4 to PL6

I didn’t upgrade from PL4 to PL5, but I intent to upgrade to PL6. The process seems to be quite simple. My question is about the database. Should I save my PL4 database and restore it in PL6?

No, PL6 will create its own database from the old.
A backup of the old is not useful but will avoid a missed, you never know.