If you made a backup of your iPhone, and you wanted all the content on your iPhone to carry over to your iPad, you should have restored the iPad from that backup. Otherwise, you will need to download them individually.
Open the App Store, and you will find a "Purchased" tab in the bottom right. You can tap the "Install" or cloud icon to download apps. If the app is universal, meaning it's designed for both iPhone and iPad, the iPad version will be used. If it's an iPhone-only app, you can still download it, but it won't run in full screen, the screen will be scaled down to iPhone size. You can tap "2x" to magnify it but then the picture isn't as high quality.