we use our tractor with a 12 inch digger bit to drill the holes down several feet.....then we round it out by hand.....mix that dirt with mulch and that new dirt that has all the vitamins...........put water in the hole......put some mixed dirt in the hole and plant the tree so it planted according to the grower's guide........they need 25 to 30 ft apart in a straight line because it is easier to cut the grass. Keep at least 2 trees the same near each other for cross polination. Soak it well while you are starting the next hole.
If you have a deer problem you need a 6 ft plus fence or use soap bars and that keeps them away. We have a severe deer problem. We also had to put chicken wire cages around them with 2 stakes 1 stake holds the tree to stand tall the other to hold the wire in place.
Depending on what time of the year that you plant........in the fall after the leaves have dropped, you need to spray with dormant oil to kill any larvae that might be on the tree. I only do that in the fall as I like the trees to not have chemicals in the fruit. Avoid plums because they are subject to black knot disease. I had to take down 22 plum trees and do peach instead. good luck with your orchard.