Okay, it's still not clear what you're asking. No need to be rude.
I assume you're trying to say is you want to add space to drive C from drive A, not transfer files, right? Would have been helpful if you told us they were the same drive, I assumed they were different hard drives since you didn't specify.
Only way to do that would be to edit the partition sizes then, which is difficult to do while you still have data on them. Normally I would recommend GParted, but I can't remember if it allows you to resize without jeopardizing data. EASEUS Partition Master claims it can do it, but I have no experience using that software.