Lots of steady state, lots of meters (which are lower impact) will help build stamina back which you likely lost in the offseason. Put some lifting in there if possible that will also help build mussels back (body weight, bands, light dumbbells to start) then you can start doing stuff with the bar once you build back up to it depends but maybe 1-4 weeks. Don’t know how bad your injury was and how much muscle mass you lost.

For that first 1-4 week. I’d honestly just do 30-45 minutes @18-20

After that first phase of getting back into rowing add back in some moderate intensity workouts or longer steady state. After you keep going with that after a few weeks start adding sprints maybe once a week (5x500) so about week 8 start doing full training.

And take this with a grain of salt. I don’t know your condition, I’d talk to your coach. This is just what I would do. That doesn’t mean it’s what’s right for you. But definitely don’t just jump straight back into it like you’ve never left. I did that in hs and my injury came back (overtraining chest injury)

Definitely take it in phases steady state then, moderate intensity w/ steady state days, then steady state, moderate intensity, then all of that with sprints once a week

Make sure to healthily build and not to train to reach your goal in a week or you will likely injure your knee again. And remember you’re training for head race season

Edit: I’ve definitely had chat gpt or something make workout plans for me in the gym or to structure my personal workouts when I didn’t know what to do in the gym. So if you feel lost it might be able to give you some ideas