Hi
You will need a male or female adaptor. Female is used more often.
The female adaptor has an internal thread in which you screw in a bush from inside the socket, the male has an external thread and a lock ring.
https://www.screwfix.com/p/tower-fem...ack-of-2/70059
https://www.screwfix.com/p/tower-mal...ack-of-2/46442
Use a dab of silicone to seal the conduit and adaptor. If you can enter the socket from the bottom to prevent ingress.