where do i get boxes

For smaller things, you can order USPS Priority Mail boxes on-line for free. Your postman will deliver. Note that not all are the "fixed rate" ones. Those are generally lower shipping, any weight to 70 lb, "if it fits, it ships". Also, USPS has ~1/2 normal parcel rate if in the same zip code "region code". For long items, like trim, many recommend Greyhound.