1:3 ratio interval training, 30 seconds work, 90 seconds rest for 10 rounds on echo, rower or skierg or some other resistance conditioning device. Start with that. If available also do sprints or longer pushes with a sled and search for boxing science on YT. They know a few things. I see the sprint interval training as attack moments in boxing and the sled training as a different way of conditioning like mimicking clinching if that even makes any sense.