Greetings Windy,
Yes, you absolutely can transplant these young pine seedlings from your planters to a more amenable planting medium such as a 3-5 gallon flower pot...for starters.
The most important aspect regarding the transplanting of young seedlings is to make sure you get as much of the root system as possible - especially the fibrous roots (fine roots). If your planters have been dry, it would behoove you to give your planter a good soak to make sure the root system of the young pines are moist and vigorous before lifting and transplanting.
