You'll need to compensate for spped loss. Generally it needs to be processed as a positive reversal. This is tricky because you don't know how it has fared. There are directions, but you need to remove the remjet backing using a solution of sodium sulfite (1 T per liter) and then develop in D19. You bleach it and clear it, and then re expose to room light. Then develop in anything (reuse the d19) for the positive image. If you're off you won't get good images and blow the highlights or shadows. It's risky at best.