If you add this ship as "merchant" in the roster, as a ship of MFM, it will appear randomly in the campaign. Then, it will appear alone in the seas or as part of a convoy. If you can live with the Pamir in a convoy, no need of scripting with the ME.
Best regards.
Fitzcarraldo
Note: As Jimbuna, I have the Pamir scripted, but it sails in a fictional journey from Kiel to the Caribbean seas and return - 1939-1941.