My IPhone XS Mac and MacBook Air are not want to use WiFi. But it use only mobile data only. It read the safari cannot have or found the server, what will be the problems to both

Check your WiFi Router / Modem for --> Recommended settings for Wi-Fi routers and access points ...

Connecting to Wifi is the first part and then getting connected to the Internet is the second

1. If you connect to Wifi, doesn't necessarily mean you are connected to the internet. If you are not connected to wifi could be a problem with iPhone settings or Router/Modem Settings
2. If you are not connected to the internet is the sole issue of Router / Modem Settings. Contact your ISP immediately

However --> Connect iPhone to the Internet - Apple Support