I have a 250GB SSD boot drive and a 1TB SSD, both of which are NVME. I’m buying another 2TB NVME and I don’t know how clone drives so I’m planning to ask the store to clone the contents of the 1TB drive to the 2TB drive, then the 250GB drive to the 1TB SSD and use it as the new boot drive. I’ll use the 250GB SSD as an external drive. Since I’m replacing the drives, I’m not sure if cloning the drives will also clone the drive letters. If it doesn’t, do I need to bring my PC to the store to change them, or can I just remove the drives and bring them to the store? Once the cloning process is done, can I take them home and expect them to work without further configuration?"
If you clone a drive, remove the old one and attach the new one, yes it will have the same drive letter and Windows shouldn’t notice the difference.
Really best do it yourself. In fact, most drive manufacturers have tools just for that, if you don’t feel like searching for 3rd party tools.