Your particular K30 won't have an isolated power supply so direct video input conversion would not be possible without a lot of work. The easiest and cheapest solution would be an eBay modulator (they can be bought for around £16). You can preset the modulator to any channel you want between ch21 and ch68 and then connect video and audio signals via SCART or Phono.
One of these
https://www.ebay.co.uk/itm/Dragonsat...2cca18cec8daec will probably do the job