you can just simply upgrade windows 8 to 10 w/out formating/deleting your unit.
If your drives had been partitioned. your files is safe..
It's better to format your unit to delete/remove unwanted viruses. you know to freshen up hahahah!
Safer way is to get your files back up. you know safety first.
like what master senpai KINJAZ said.. try to search on google.