Those don't look too bad at all. If you do not feel a difference than the marks did not go past the clear coat.
@MRRSM provided the perfect video for you to watch!
If you do not have access to an electric buffer as ChrisFix used, I would follow all of his instructions and disregard the rest of my post. If you do however have access to a buffer I recommend following the instructions below. It'll look great and take half the time.
I don't suggest using all of those higher grits of sandpaper at all. I would go to your local parts store and get an assorted pack of sandpaper that contains at least 600, 800, and 1000 grit sandpaper. You should be able to get them out starting with 600 grit. I would take a close up picture of those scuff marks before you start so that you know exactly where they were and how the scuff marks looked. Honestly, you could just start with 1,000 grit dry then wet sanding and you won't notice the difference. You would just be sanding with the one grit a little bit longer.
I also do not suggest sanding the entire door panel either. You'll end up having to sand/buff the entire vehicle if you do that. I would just sand exactly where the marks are connecting them all with your sanding strokes though. So you have one area to work with and not 3-5 smaller areas.
It looks like you would have about a foot or so of area to work on from that picture. Make sure you stay a few inches away from that door handle or any other panel lines/moldings near those marks with your sanding as well.
Start by taping off the area that you plan on sanding into a square around those marks. 600 grit is key as you need to get the scuff marks to "disappear" with the 600 grit. Once the area you chose looks uniform, jump to 800 grit and do the same. Make sure that you are not sanding very long at all on the area you chose. You do not want to eat through your clear coat. I would sand for a few minutes with each grit, you do not want to eat through your clear coat.
At 800 grit you are still sanding dry to start but, add water to wet sand now. Only sanding for a few minutes again. After a few minutes of wet sanding, switch to 1,000 grit. At 1,000 you can start dry and then wet sand if you want. I would just start with wet sanding using 1,000 grit.
Once you finish wet sanding with 1,000 grit. Now you would need to start the buffing process. I would just follow ChrisFix's guide and he did a good job with his buffing instructions. Make sure that you rinse and wash that compound off IMMEDIATELY though. That stuff will cake on if it's in the sun.