It's a small (and rather nice) town on the outskirts of Bialystok. Google it.
List? The name and address of the orthodox cemetery in Supraśl is:
Podsupraśl, 16-030 Supraśl, Poland
As far as the graves go, I would contact one of the following:
The Orthodox Monastery in Supraśl monaster-suprasl.pl
Supraśl town itself suprasl.pl
Tel # & email at bottom of page.
At this time, I don't think the graves have been catalogued in this town for easy searching online.
You have to contact the town (link above), assuming they were buried less than 100 years ago. Otherwise, you have to go through the state archives
This town's cemeteries are not yet archived online. To have someone else do this search for you will cost them time and money, so you would have to pay for that service. Or you can do yourself and contact the town yourself.