Download macOS High Sierra 10.13.6 Combo Update - Apple Support
You’ll end up with HighSierra.dmg on your Desktop, mountable and bootable. download+macos+high+sierra+10136+dmg+mac+install
High Sierra is the last macOS to fully support 32-bit apps without issues. If you rely on old versions of Photoshop, Microsoft Office, or specific niche software, High Sierra is the best OS to stay on. Upgrading to Mojave or later will begin warning you about 32-bit incompatibility. Download macOS High Sierra 10