Easiest way to find the storage engine being used currently in from mongo console.
Inside mongo console, type (You might need admin access to run this command)
db.serverStatus().storageEngine
If It returns,
{ "name" : "wiredTiger" }
WireTiger Storage engine is being used.
Once it is confirmed that wiredTiger is being used then type
db.serverStatus().wiredTiger
to get all the configuration details of wiredTiger.