Reddit mentions of Whirlpool 3048KITRC 30-48KITRC Gas Range Connector Kit, white

Are you comfortable with and capable of working with gas lines? If not, call a plumber or the gas company and let them deal with it. Typically, the gas company will be cheaper than a plumber, but not all gas companies will service in home lines/appliances. Some will provide materials, others will require you to do so. At the very least, I would get a quote or two. Sometimes it's cheaper and easier to let someone else take the liability. If you decide to DIY, head to a big box retailer and get one of these or these. You'll need that at a minimum. If you can remove the gas line from the flare fitting attached to the valve, you should be able to re-use it. The flare fittings themselves are fine to re-use, it's the flexible gas line that you don't want to re-use. If you can't or prefer not to re-use the flare fitting, I would also get a new gas valve as well as the threads on the existing one are likely damaged. The pipe should be 1/2" NPT. Make sure you can turn off the gas either at the meter, or somewhere upstream of the stove before you attempt to remove/replace the valve. You will need either some thread sealant or Teflon tape (not both). Only seal the threads on the NPT to NPT connections.