Old App not working

I had an App to connect external memory (called i memory link) that was working well with my old iphone 5, and worked fairly well with this iphone 7 as well , however it stopped working on the new iphone 7 while still working on the older iphone 5 , although i did not update my Phone software but perhaps tried updating the App. It gives a message"Unable to install i memory link:The App is no loger present on App store" and i can no longer use the external memory data that i saved. I tried other programs but all did not work