You may add the models key to your config/shopr configuration file:
/*
* The database models. You may swap these with your own models, just make sure they extend the
* corresponding package model rather than the standard Eloquent model.
*/'models'=>['Order'=> Happypixels\Shopr\Models\Order::class,'OrderItem'=> Happypixels\Shopr\Models\OrderItem::class,],
However, this isn't necessary if you don't intend on using your own order models.