It depends on how your SMS is deployed today. Ideally, it runs as a virtual machine. Then you clone it and keep the original for a rollback. On the clone, you can perform a new installation or an inline upgrade. See the R80.10 Upgrade and installation docs for more details.
I personally prefer the new installation, since you get rid of all old and unwanted crap on your SMS.
Independent of your deployment, first you run the R80.10 migration tool pre_upgrade_verifier on your curent SMS to check if the DB is clean and R80.10 compliant.
Then you cleanup the DB if required.
Then you do the migrate export on your current SMS and migrate import on your fresh installation of R80.10 SMS.
If anything goes wrong with it, you can easily switch back to your old SMS by activating the old VM.
Hope this helps