Hello! Thank you for your feedback!
To use these on Unity, you just need to import the FBX files(or the entire folder, it will make things easier), then click on the model you want to use and on it's Inspector click on "Materials" and then click on "Extract Materials..." and choose where do you want to extract the material inside your project folder.
Select the material you extracted and on it's Inspector you need to change the Rendering Mode to "Cutout", and then you can drag the correspondent PNG texture(it has the same name of the FBX model) to the material Albedo, change the Alpha Cutoff to 0.1 and disable Specular Highlights and Reflections.
Now click on the PNG texture and on it's Inspector you just need to enable "Alpha is Transparency" and disable "Generate Mip Maps", also change "Filter Mode" to "Point (no filter)". This will make the texture look pixelated instead of the blurry standard.
I hope I made everything clear and it works great for you! :)