This is part of the NServiceBus Upgrade Guide from Version 8 to 9, which also includes the following individual upgrade guides for specific components:
Transports
Other
New package for MSMQ support
In version 3, support for bridging MSMQ endpoints is now provided by the new NServiceBus. package. Remove any references to NServiceBus. and update the bridge configuration from:
var msmq = new BridgeTransport(new MsmqTransport());
to:
var msmq = new BridgeTransport(new MsmqBridgeTransport());