The first thing to do is to check the card is in the slot properly. Secondly, check which version of Android you're using. In Settings>About Device will tell you that. Any version older than 6.0 cannot nominate the SdCard as either Internal or External (Portable).
Then in Settings>More then Storage to see how much space you have.
I'm not familiar with version 9 but the option to set the card to Internal Storage wll be available in Settings>More>Storage unless the menu structure hs changed.
That said, it would normally be set to Internal by default so the problem might be with your SdCard.