Any version of SDK 3 should work. I’d recommend the latest. See Compatibility | Couchbase Docs
While you’re thinking about upgrades, note that Couchbase Server 6.6 has already reached “end of maintenance”, and will reach “end of life” in October 2023. Reference: Enterprise Software Support Policy | Couchbase
With a recent version of SDK 3, it’s no longer necessary to put the trusted certificate in a pfx file. Instead, you can just copy the certificate from “Couchbase > Security > Root certificate” into a file, and point the SDK at that file. Example: Use Certificate in JAVA SDK - #3 by david.nault
Thanks,
David