If you have Stolen Device Protection set to “Away from Familiar Locations”, when you try to turn it off, keep tapping Try Again until you are prompted with entering your passcode, thus turning Stolen Device Protection off.
If you have Stolen Device Protection set to “Always”, you will have to go a longer route to turn it off. Open iCloud.com/find and log in with your Apple Account, then select your iPhone from your list of devices, then select “Remove from Account.” That will turn off Find My and the Activation Lock, and alongside Stolen Device Protection, which is tied to that.
If you cannot get your 2FA Verification Code to do so, there are a few other ways to get it. First, use one of your additional Trusted Devices already on your Apple Account. Second, use one of your pre-designated Trusted Numbers. Third, you are looking at Account Recovery. Alternatively you may be able to use a Hardware Security Key if you already had it setup in lieu of a Trusted Number.
You can then turn Find My back on and Stolen Device Protection will stay off. Keep in mind there may be a 1 hour security delay for both.