First, 6.0.6 was recently announced. You should probably be upgrading to it.
Second, please convert your Trees from BSDDB to SQLite with 5.1.3 before upgrading to version 6
A BSDDB database plugin is not necessarily bundled with Gramps anymore.
You are still using 5.1.3? Your previous post in August was asking about upgrading to 6.0.4