I want to take out of USB enclosure but I heard that some drives are encrypted by by USB connection and I will not be able to read the drive after connecting in straight to the computer.
Actually, My Book drives made before the use of Smartware should not have any drive encryption so you will be able to access the data on the drive by plugging into the computer directly.
If you already started to copy off the drive then just keep doing that.
As for your last question, yes, you will be able to reformat and repurpose the drive without any encryption getting in the way. It is just a standard 3 1/2" hard drive inside the enclosure.