Hi...
What you are trying to load is a project file, not the individual clothing items.
So try loading the project (character and clothing) and then select each item of clothing in Scene Manager and save them to your custom clothing library by clicking the + ADD button at the bottom of Content Manager. Then start a new project with the character you want and apply the clothing to the character directly from the clothing library (see below).
Peter
Forum Administrator
www.reallusion.com