It really depends on the amount of files you want to move...if there are a lot, doing manually it's going to be a considerable effort and you might have errors when doing that move. As an alternative of the manual move, you could create a PowerShell Script to make the move and add errors control to the Script.
In regards of migration tools, Sharegate, AvePoint and Quest are good ones but of course you might also find other tools cheaper for the scenario you have here
