To install macOS High Sierra 10.13.6, your Mac must meet the following system requirements:
High Sierra automatically converts SSDs to APFS. To check: macos high sierra 10136 dmg install
3.1. Obtaining the DMG The user must acquire a trusted DMG source, ideally from a previously purchased copy via Apple ID or a known-good backup. Unverified third-party DMGs pose significant security risks, including rootkits or modified system files. A SHA-256 checksum should be compared against known community-sourced hashes. To install macOS High Sierra 10
Here’s the short story and practical answer: To install macOS High Sierra 10.13.6