You might consider a story centered around a mystery. Maybe a disappearance or a crime that needs to be solved. This can keep readers on the edge of their seats as they follow along with the investigation.
One way to write a fantasy fiction story is to start with a prophecy. For example, there's a prophecy that a chosen one will be born with a special mark and will defeat an ancient evil. The story could follow the journey of this chosen one as they grow up and discover their powers. Or, you could create a world where dreams are real and people can enter other people's dreams. A thief could use this ability to steal secrets from the rich and powerful. Additionally, you could write about a group of adventurers on a quest for a lost city full of treasures and magic.
Set it in a different time period like the 1920s. Cinderella could be a flapper girl who dreams of going to the big jazz parties but is held back by her step - family. The 'prince' could be a rich jazz musician. Instead of a glass slipper, she might leave behind a beaded headband. And the fairy godmother could be an older, wise jazz singer who gives her the confidence and the right look to attend the party.
You can get story ideas by observing your daily life. Simple things like a conversation you overheard or a strange event you witnessed could inspire a story.
Imagine a world where people can exchange their dreams. A person who is always dissatisfied with their own dreams decides to trade with others. But they soon realize that each dream has its own problems and that the grass isn't always greener on the other side. Through this experience, they learn to appreciate their own dreams and the unique experiences they bring.
Use isolation as a key element. For example, a lone lighthouse keeper on a desolate island starts to notice strange lights in the ocean at night that seem to be getting closer each day. Another idea is to have a character lose their senses one by one. First, they lose their sight and then start to hear strange whispers. This can build a lot of tension. You can also write about a town where all the children start to disappear mysteriously, and the adults are too afraid to look for them.
Read a lot of different books and observe the world around you. Ideas can come from anywhere, like a strange conversation you overheard or a unique place you visited.
You can get ideas by observing your daily life. Something as simple as a conversation with a stranger or a unique place you visit could spark inspiration.