Hi, i have a mac 10.12.6 can i upgrade it to High Sierra?

Yeah, all macs that support 10.12.6 also support High Sierra.

Follow this guide for how to install:

How to get old versions of macOS - Apple Support

Depending on what mac you have you might be able to install a newer version as well:

List of compatibility: Mac OS from 10.10 … - Apple Community

Good luck!

If you have a Late 2010 or later MacBook Air…

Open in Safari.

https://apps.apple.com/us/app/macos-high-sierra/id1246284741?mt=12