If I recall correctly the Stormrider is threaded M10x1 which is what the Sumatra adapter is:
*Make sure to use a suppressor one caliber size up. Works really well and reduces the chance of pellet clipping.
Diana uses this thread for a lot of their rifles and pistols.
I recommend the KOI 1/2x20 for the Stormrider.
https://donnyfl.com/collections/ldc/products/1-22-x-7-inches-koi