You are trying to use a crop frame camera to photograph a 24x36mm film, so you need to be able to achieve 1:1.6 reproduction ratio or 0.62x,
Your lens can get up to 1:2 or 0.5X, so it would not fill the frame of your camera as is...so you need to use suitable length of extension tube (dependent upon what FL setting is on your zoom)
- 50mm extension tube on 50mm FL focused at Infinity gets 1:1
- 50mm extension tube on 100mm FL focused at Infinity gets 1:2
- 50mm extension tube on 200mm FL focused at Infinity gets 1:4
I am not familiar with optical behavour of 100-400mm lens at macro distance, but a 'true macro' lens is
A) optically corrected for flat-field reproduction with
B) little pincushion/barrel distortion,
and a lot of so-called 'macro' lenses simply 'focus close' with little correction for the other characteristics of 'true macro'
you need a way to position your film to be duplicated, with careful control of camera-to-film distance and with an even source of transmittel color alanced light thru the film.