Please I can’t find software update on my Apple phone

You need a Wi-Fi connection, no add-on VPN app installed while updating, sufficient free space, or you will need the use of a Mac or Windows computer.

Inferring much about your particular situation, you’ll probably best use a computer to manually perform the update.

Per what Apple writes about that: If you can't see the update on your device, use your computer to update your device manually. Learn how to update your device manually if you're using a Mac with macOS Catalina or later, or if you're using a Mac with macOS Mojave or earlier or a Windows PC.

Go to settings - general - software update.