How do I back up Xs max iPhone without Wi-Fi and how do I know it’s complete
How do I backup my I phone without Wi-Fi and how will I know its
iPhone XS Max
Question marked as
There is no option to backup an iPhone Xs Max to iCloud without wi-fi.
Later models (iPhone SE 3rd gen and iPhone 12 & later) can be if the carrier gives the option. See the following from Back up iPhone - Apple Support
Note: On models that support 5G, your carrier may give you the option to back up iPhone using your cellular network. Go to Settings > [your name] > iCloud > iCloud Backup, then turn on or off Backup Over Cellular.
An option that doesn't require wi-fi is to backup to a computer. See:How to back up your iPhone, iPad, and iPod touch - Apple Support