Another way is to set up a UWorld property in your blueprint of type SoftObjectPath. This allows you to select directly a level from the content browser without relying on strings, which are error-prone.
The additional benefits are that if you change your level name, it will be propagated to your property, you won’t have to go in your blueprints to manually update the names.
And since it’s a soft object path, the level won’t be loaded so you don’t have to worry about memory.