Help replacing textures for metal gear solid 3 3d (citra)

[SolidArbiter]

I am trying to replace certain textures but I am having trouble. From what I learned, for this I have to create a png file with the correct aspect ratio and format but it can have a higher resolution and it needs to have the correct file name. I tried to unpack the game until I managed to get to unpacking slot.dat (using shagohod.exe although it didnt specify the 3ds version), where I read that other mgs games keep their textures, but I only got from that 600 folder and the majority of them had an .row file, I also saw some .img .mdb and others. This is where I got stuck because there is no image and I cant unpack further. I am aware of the HD project for this game but it doesnt have the texture I need.