Depending on where you are you might also need to protect them from munching creatures and frost heave. In Nature there are usually plenty of seedlings to cope with the natural thinning process but you've only got three.

You probably also need to mix in some soil/duff from the area where the parents were growing because many pine trees need to work with their own brand of soil fungi to grow well. You could also mulch with old needles or bark chippings but not too close to the stem.

If tall and stately is the result you want them you need to plant them quite closely in three to five years time, when they've developed a good root system. Many pines, when planted with a lot of room to spread, do just that.

In the year before you lift them you will probably need to undercut the roots so they can first grow new feeder roots and so you can lift them later with least stress to the trees. Check with your local forestry people about the optimum planting time/s for the species you're growing.