How to upgrade the iOS of mac book pro

FYI, iOS is Apple's operating system for their iPhones. OS X, or more recently, macOS is Apple's operating system for their computers.

Regardless, which exact MacBook Pro model do you have? Is it currently running macOS High Sierra (10.13) as per your tagline?

To find your exact laptop model, you can either use the information in the Support article you arrived here from or by selecting the Apple logo on the macOS menu bar, and then, selecting "About This Mac."

Below Only Applies to Apple Computers and not to iPhones / iPads

The Age of this computer will Govern what newer version of macOS it will Qualify to install. 

Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.

Safari will open a redirect and open the Apple Store where the download can commence.

Does this computer appear as Listed and qualifying for an upGrade to a newer version of macOS ? 

If Yes, suggest having at least 50 GB of Empty Space on the drive.

It will allow the Full Version ( about 12.xx GB ) to download, expand and then commence to install.

If there is Third Party Security Software installed - remove it.

It will interfere with both the download and installation process.

The below links will help identify which version of macOS  this computer may Qualify to run.

macOS Sonoma is compatible with these computers

Computer Qualifying for macOS 13 Ventura 

Computer Qualify for the Monterey upgrade

macOS Big Sur 11 hardware requirements

macOS Catalina 10.15 hardware requirements

Make Time Machine Backup  before doing any upDates / upGrades