sub posts to parent post

WordPress posts are non-hierarchical and therefore cannot have child posts

Most likely the model in question has a hierarchical category(taxonamy) associated with it.

EG:
Country > Technology type > product type > model

Using the catagories like this will give you the required url structure once you assign a pretty permalink structure http://codex.wordpress.org/Introduction_to_Blogging#Pretty_Permalinks

tech