scope adapter

I would not use an adapter. Srpingrr/gas ram rifles such as yours have quite a bit of recoil and can knock a scope loose if it is not well secured. It would be better to buy a set of scope rings to fit your set up (30mm scope with 9-11mm dovetail rail?). Adapters would add one more point for something to come loose. A set of rings is probably in the same price range as adapters anyway.

Now, with that said, Pyramyd Air sells an adapter from UTG that is made for Diana rifles. This adapter is said to eliminate scope shift, fits the rings your scope came with and gets good reviews.