Wii U Pro controller analog sticks not recognized by Mame in RetroPie

[ogbuehi]

Pi Model: 3
Power supply: 2.5A
RetroPie version: 4.2.7
Built from: ??
USB devices: Rii Keyboard Mouse Combo model RT518 (wireless bluetooth) and Mayflash Wireless Wii U Pro Controller to PC adapter
Controller: Mame

I apologize if this seems like a simplistic request but I'm fairly new to the the Pi world.
The issue that I'm having with the Mame is that I can't get it to recognize the analog sticks when I go into the in-game Mame setup menu (the one you get to by pressing tab on a keyboard). Some things I've figured out based on my own tinkering, Google and Youtube searches:

1. There are apparently different versions/types of Mame. On my other Pi (I have 3), that version of Mame was easy pretty simple to map my Wii U analog sticks in the Mame GUI setup menu. I notice my problem Pi however, that GUI menu looks different and it doesn't recognize the analog sticks when I try to map them (it does recognize the D-pad and the other buttons).
2. I have not been able to truly determine what version Mame I have on the Pi's.
3. I'm open to the idea that I may have to just try and install that same version of Mame on the Pi that I had no issues with. However, I've realized that, through research, the roms may not work with the different version of Mame. I'm not super comfortable trying to delete the emulator and installing the different version along with moving all the roms (2k+).
4. If it's possible, I'd like to just edit a config file with commands/text for the inputs. I've done this with RetroArch because the GUI setup menu for some reason would not recognize the start button on the Wii U controller (annoying problem because I couldn't get the standard start&select button combo to exit the emulator working). I simply figured out (through some heavy research) how to edit the config file with the necessary text to force RetroArch recognize the start button. What I haven't found is exactly what config file I would need to edit for Mame (I've been looking through all the config files I can find on my Pi that are Mame related with no success). I also haven't found the text you would need to input if I found the right config file to edit.

I know that was a mouthful but I appreciate any help anyone can offer. Thanks in advance.