What do you mean? It's a simple question, are you using the drive to play Wii U games from the Wii U menu, or Wii games using an USB loader? There's nothing to check.
There are a few routes you can take:
If you want to play Wii U games off the drive then there is no way to simply access the contents from a PC (and why do you want to?), since the Wii U format is encrypted and proprietary. Dumping tools exist that can dump files from a Wii U formatted drive, but they're of limited usefulness, mainly useful if you need to get save data or whatever off the drive and can't do it on the Wii U for whatever reason. You can get files on and off the drive more easily on the Wii U itself, but there should rarely be a need since games are installed using WUP Installer or NUSspli, and can be deleted from the Wii U settings.
However, you can play Wii U and Wii games off the same drive using Wii VC injects, it's just a little bit more of a pain to add games to it since they have to be installed with WUP Installer or NUSspli on the Wii U, instead of using Wii Backup Manager to quickly copy the files. This is generally the best route to take, since it's the only way you can run Wii U and Wii games from the same drive.
The last route, if you are just trying to play Wii and/or GameCube games would be to format your drive as FAT32. Alternatively, this tool can convert a WBFS formatted drive to FAT32 keeping the games that are on it:
https://gbatemp.net/threads/wbfs2fat-py.291320/ (assuming your drive is already WBFS, which is why I'm asking the question)
For this use case, the use of uStealth is recommended or the Wii U will nag you to format the drive constantly. Accidentally allowing the Wii U to format the drive will wipe it and change it to the Wii U format.
https://gbatemp.net/threads/ustealth-wii-u-format-disk-nag-workaround.352786/
Must hide the drive using the tool before plugging it into the Wii U and when you want to access it from the PC to add/delete games you must unhide it again.
For the record, Wii Backup Manager can access a WBFS formatted drive and add and delete games from it. You just won't be able to access the drive from other apps and you won't be able to put anything but Wii games on it. So it's not really recommended when FAT32 is an option.
The part about converting a WBFS drive to FAT32 applies if you've been using this drive to play Wii games from a USB loader, and you want to keep the games on it. Otherwise you can ignore that part.
If you're trying to use the drive for something else, like put ROMs on it to load in emulators, or put homebrew on it, the drive must also be formatted to FAT32, which means Wii U games can't be played off it. ROMs, homebrew, etc. can be put on a SD card instead since they aren't that big.
I hope I explained everything well enough so you understand how things work.