Johnp is absolutely correct. If you want to use the SMDR to post priced calls to the PMS, you need to first connect a call accounting system to the Mitel SMDR port. The CAS will have another serial port (output) which you will use to connect to the PMS's call accounting port. The raw SMDR data is of no use (not to mention the wrong format) to the PMS.

The 3300 will also have another serial port that will communicate directly with the PMS system. It uses this port when a guest checks in or out to assign the guest name to the room extension and to allow or deny local and/or long distance services.

You need make sure (on the 3300) which port is set up for interfacing the CAS and which port is set up for interfacing the PMS.