Have you sourced a voltmeter and measured the open circuit voiltage of a film pack? Do you still have a supply of film ( I know, we all hope Polaroid is coming back into production)
Otherwise, if you are electronic handy, and going to modify this camera for other purposes (a noble calling, in my book) and have no film pack to measure with, then:
Hook up a filtered full wave AC-DC rectifier to the input on the camera, and feed it AC from a variac, starting at 0 Vac. Peel the camera apart an look at the polarity of any capacitors inside the camer's pcb to figure out which pad is positive and which is negative, as there may have been no provision in the original design to deal with the possibility of revered voltage with a film pack power source. Hook up the dc leads, and start to step up the voltage on the variac to give you increments of 1.2V DC coming out of the rectifier. At some point the camera will power up. Do not go higher than the first increment at which the camera will power up at.
Unless you have a powerful DC supply, do not try to fire the flash. Batteries can supply way more short circuit current than most DC power supplies can the instant that an electronic flash capacitor draws when it first starts to charge after being discharged.