So I took my 96 x90 to get it smoged and it passed the visual , actual smog was fine but it failed the obd2 test. I flat towed it to the smog place so I had disconected the battery. The guy told me that is probably why it failed the obd 2 portion. So my question is how long do I need to drive the car before the ecu will record all the necessary info to pass that portion of the test?

Did he say why it failed the ODBC II test?  Usually it is because of an error code being thrown.

Usually an hour or two is enough for your motor and computer to figure out what is going on.  There are a few codes that will clear themselves once the vehicle has been started and stopped a couple of times.

I think he said it was in self test mode?

I had to drive a car for about 10 days before it went thru the
self test

Wild

If you disconnected the battery then all the tests will report 'not ready'. How long you need to drive it for depends on each test, some require as many as three 'drive cycles'.  Generally you need to drive it fully warmed up and above 50mph to achieve each drive cycle.