Could you tell me more about your set up?
Most of the time you just need to download the knots implementation, and copy the blockchain data over from the directory associated with your core node to the correct place in your new bitcoin knots files.
If you have something like umbrel OS or start OS, this is even easier, you just 'pause' the bitcoin core node app, download bitcoin knots. It should figure out what to do itself.
Please don't hesitate to ask me about anything that doesn't make sense!