I'm a bit confused as to where you are getting the numbers you are asking about. Like any new tank no matter how large it is, it needs to be cycled. You can do this fish in style or fishless style. Using such a small amount of Guppies in a tank that large is going to take months for it to cycle. You can shorten that time if you go fishless. OR if you are moving the fish from one of the 6.5 tanks, you can take the filter material, the gravel and all the decorations and move them into the 40 and your tank will be instantly cycled for the amount of fish that were in the 6.5. ( To be clear, you want to put the filter material in the bigger filter along with new material so there will be more space for the biological bed to grow.) At that point you will be able to add more fish however, it should be done slowly and in small quantities as the biological bed will need to grow to handle the new ammonia load.
As for moving fish over to the new tank, if the water parameters and temperature are the same in both tanks, they can be netted and moved directly. If there is any differences, you can Bag acclimate them as I described before. Since you are moving fish that are already used to your water, there is no need to drip acclimate. Just so you know, it's never a bad thing to drip acclimate but it's a matter of whether it's necessary to do. With shipped fish, it matters. From a home tank to another home tank of similar water, it's unnecessary.