How to get rid of server and make into solo world?

I created a server for me and my friends to play on as all of us did not want to pay for a server. After a while I have been the only person on the server and making progress. So I asked my friends if they were going to ever play again on the server, which the all said no to. So I have been trying to figure out how to copy the world on the server and make it into a solo world. I want to do this as I made a lot of progress and don't want to lose it. It also has become a slight hassle to go to the Aternos website just to wait a good 2 minutes and then play. On top of that sometimes the server would crash for no reason at all. This could be all avoided if I made it into normal solo world hence why I want to make the server into a normal solo world. Any help on how to do this this?

Thanks Adriel, It worked!