Ok this is going to be quite long and won't cover everything.
Persona 3 Reload uses the Unreal Engine so you can rip it with things like UnrealPakViewer and UE Viewer. However, the most useful one to me is FModel, so that's what I'll explain.
First, you'll need the actual files. On Steam, they'll be in the Steam folder. On my computer, that's in Program Files (x86). In there, there'll be a folder called steamapps, in there common, in there P3R. I haven't ripped a disk of it, but I'd imagine that it would have the files in there on it. In P3R, there's another P3R, in that Content, in that Paks. Everything will be in the pak and ucas files in that.
You only have to do this bit one, so it might not work. Just ask if it doesn't, I'll try to help. In FModel, in the top left, there's a tab that says Directory. In that, Selector should open a new tab. The Detected Game should be Paks, the UE version UE4_28, and the Directory the file path to the P3R Paks folder. Reload's AES key is 0x92BADFE2921B376069D3DE8541696D230BA06B5E4320084DD34A26D117D2FFEE. It might also ask what folder it should extract to? Just choose which one you want. Then, it should detect the 6 pakchunks, each with a pak and utoc file.
To extract things, left click. You can do this in bulk on a folder, but it'll only extract the type you chose. You probably just need the textures(.png) though.
Everything you want should be in the ucos files. I think the paks only have sounds? If you want something specific, you'll have to go on a bit of a hunt to find it. The files are split between all the pakchunks, so you'll need to look through all of them. It should be somewhere in P3R, Content, Xrd777. Xrd777 only has the japanese versions, though - the english versions are in the same place but in the Xrd777 inside either pakchunk4 or 5, L10N, en. The image files are mostly in the texture or sprite folders. Commu is the japanese name for a Social Link, Theurgia for Theurgy, and Camp is the menu.
This has a nice list of where a some things are.
Despite everything being .uasset, the letters that start the name of the file say what's in it. T is an image, and probably what you're looking for.
I'm not sure where the dialogue boxes are: they might be generated in real time instead of using a texture.
Uhhhh anyway here are some UI rips. A lot of them are white because the colour is added in real time instead of being baked into the image.
jbbartram-illu
snowghoul
pixelskylines
kaledo-art
