i need to find the APN settings

Hello.

Head to Settings > Mobile Data > Mobile Data Options > Mobile Data Network.

Depending on your region you might have Cellular instead of Mobile Data but it's the same thing.

If you are using an Apple-affiliated carrier you will not have access to that, it is stored with your Carrier Settings file. If you are with a non-affiliated carrier you will need to get the settings you need to enter from your cell provider.