How can download all apps in my iphone5c?

Why not? What happens when you try to download an App?

Your iPhone 5c is a bit old now, many apps will not support iOS 10 anymore. If the Apps require a higher iOS version, then you won't be able to download them to the iPhone 5c. You will need a newer iPhone, with a newer iOS version.

Then you won{t be able to download apps that require a version higher than iOS 10.

There's now way around this. There is no way to magically make the 10 year old iPhone 5c run new apps that require hardware and resources it does not have.

That would be like trying to run today's apps on a computer from 1994.