You don't know how to make a 3D file but you want to 3D print objects? They have thousands of individual models available all designed specifically for Blender projects.
The site hosts 18k+ models, which are searchable and sortable as well.
Free3D is also a terrific resource for beginners just starting to learn game design.
Not to mention other marketplaces have sales frequently so you could pocket a pretty penny if you keep on the lookout for deals.