The answer is a clone - a perfect copy which will boot up the system. It's best to ditch all the unnecessary stuff before cloning so run some cleaner - CCleaner and ATC Cleaner find different things to clear out.
Next, press the Windows key and R together and into the Run box, type
cleanmgr
and hit Enter. Tick to remove system files and you should see a lot more free space on the disk.
There are several effective clone utilities but I use EaseUS Disk Copy because it can handle a large source disk going down to a smaller target disk.
At the end of the process, ignore the instruction to remove the source disk but just tell the BIOS which one to boot from so you don't get two drives fighting over which is going to be C: