Are you using the same Apple ID in the App Store/iTunes that you used before? If so, have you tried signing out of the App Store/iTunes, restarting the device and then signing back in again? Have you checked your purchases history to see if the apps are there?
Purchase History Review. https://support.apple.com/en-us/HT204088
If the apps don't show in your purchases history, you need to delete them, and download them using your current Apple ID. If the apps do show in your purchases history, contact iTunes Support. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option.
iTunes Store - Contact Us - Official Apple Support. https://support.apple.com/en-euro/itunes-contact
iTunes Support – world wide https://support.apple.com/choose-country-region/itunes