Would like to check if your windows COA is windows 7 or Windows Vista?
If windows 7 COA, you can use it to update to windows 10, by fresh install, by specifying the windows 7 key.
Before you proceed, I would recommend you to backup important data and settings , e.g. to external hard disk / location.
Check for any possible BIOS updates too....
some consideration to take note is your specification of your computer, e.g. processor, RAM, etc.
IMO you should go for Win10 if your computer is able to support.
As Win Vista is generally not supported anymore
Once backup is done, you can consider to use a USB thumbdrive to create a win10 bootable media, from microsoft and perform a fresh install, which i normally do by deleting all partition and recreating it.