Should be able to do it with Wii Backup Manager.
https://wii.guide/wiibackupmanager
Set drive 1 to the WBFS folder that the folder with the two parts are in.
Then set drive 2 to wherever you want them to be.
Then change the Wii Backup Manager settings to not split the files.
Then select the game in drive 1 and transfer to drive 2