Can I do a backup without wifi

For information on backing up to iCloud without using wi-fi 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.

The other option that doesn't require wi-fi is to backup to a computer. See the Mac or PC section of How to back up your iPhone, iPad, and iPod touch - Apple Support