@Spice_1 Go with either 245/45R18 or 235/45R18. I prefer 245 for 8.5" wide wheels, I'm running 245/45R18 on 18x8.5" wheels right now on my 2021 M3P. Stock Model 3 18" size is 235/45R18 on 18x8.5" though and that's fine too.
Basically going 245 instead of 235 gives you a bit of extra width and sidewall and diameter, all good things for this car in my opinion. It still fits perfect and is a recommended size for 8.5" wheel width. Just for reference, my other Tesla came with 245 on 8.5" wide wheels, and so did my last ICE car.
@The Other Dan 245/40R18 or 235/40R18 would be very small diameter for a Model 3, don't go that small unless you have some very specific need/reason to.