You will need this adapter to add a suppressor to this airgun.
Most evanix shrouds uses the same thread size for the adapter. This one should fit: https://donnyfl.com/products/evanix-rainstorm-1-2-x-20-unf-adapter-a29?_pos=2&_sid=b77d300ac&_ss=r
I recommend the Ronin .30 1/2x20 #S18. This will quiet down the barrel report not the action of the airgun.