Have you changed country settings on your device?The apps may only be available in specific countries.
Apps may also be withdrawn from the store by the developer. Maybe the used to be sold in your country but are no longer sold there.
Here's how to request a refund on an Apple mobile device (From: Request a refund for apps or content that you bought from Apple - Apple Support - see the article for more detail.)
1. Sign in to https://reportaproblem.apple.com.
2. Tap or click "I'd like to," then choose "Request a refund."
3. Choose the reason why you want a refund, then choose Next.
4. Choose the app, subscription, or other item, then choose Submit. If you were charged for a subscription that you no longer want, you can also cancel the subscription using the directions in this article --> If you want to cancel a subscription from Apple - Apple Support ].