Just measure the ground glass. If it's 4x5, it's a 4x5 camera. If it's 3.25x4.25, it's a 3.25x4.25 camera. I wouldn't think those holders would fit a 4x5 back though. So if the holders fit, you have a 3.25x4.25 camera, aka quarter plate. Film will be cut by Ilford as part of their order. Freestyle still has Efke 100 in stock but of course that's going away. It's a hard film to find.
I cant take the back off to measure the ground glass. Although I now firmly believe its a 3.25x4.25, and I'm kinda having buyers remorse over it. I think I was smitten by the thought of that big ole negative, but honestly... how much would I actually shoot it. The Hasselblad barely gets enough exercise as it is.
or maybe cut a 3.25x4.25 cardboard or paper then try if its fit...
Usually, 3-1/4 x 4-1/4 Anniversary Speed Graphics have that shutter speed plate on the top of the camera and 4 x 5 Speed Graphics have the plate on the side. Your camera looks like 4 x 5.