As someone who has moved her fish like 50 times, I have to tell you, I HIGHLY RECCOMEND my way of moving them.
Get medium sized plastic jars, I used peanut butter jars, with holes punched in the lid. Scoop each fish into his own jar, fill it about 3/4 full, and add whatever you like - bag buddies, java moss, etc.
Get fairly shallow boxes, that are a bit taller than your jars. Crumple up newspaper and cover the bottom. Place the fish in their jars on top of it. Stuff crumpled newspaper all around the jars - make sure there is newspaper separating each fish from any other fish, and every side it might touch. Pack it to a decent tightness. Close er' up.
This has been my favourite way to transport so far. At first I tried leaving them in their original tanks and lowering the water to halfway - this is not so good. The water sloshes around too much and the betta goes FLYING, and even worse the car might get all wet. It's a no-no.
Then I tried just putting them in jars, but they got scared because of all the commotion around them, and it would be hard to carry more than 1 jar around.
Finally, I decided it's best for the fish to put them in a padded box.
Good luck with moving them all!!