Software update is my iPhone

Update your iPhone, iPad, or iPod touch

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.7

• If you have an iPhone 6S through 7, or SE 1st generation, you can update to 15.7.7

• If you have an iPhone 8 or higher, or SE 2nd or 3rd generation,you can update to 16.5.1

Go to Settings > General > Software Update.

This link will show you how to update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone or iPad - Apple Support

This link will show you how to update using your computer -

Update iOS on iPhone - Apple Support

Hello~ Take a look here by clicking on below...

Update your iPhone or iPad - Apple Support

If you are having issues...

If your iPhone or iPad won't update - Apple Support

Post back if needed and take care.

~Katana-San~

I've already given you the answer.