Quick fix
Downgrade your autoprefixer to version 9, use
“autoprefixer”: “^9.0.0”
in your dev dependencies.
More details
PostCSS was updated to version 8, however, PostCSS CLI has not yet been updated to handle PostCSS plugins which use the new PostCSS 8+ API. Autoprefixer uses the new PostCSS 8 API since version 10.
This is documented under known issues in the PostCSS GitHub page.
Once PostCSS CLI is updated to handle plugins that use the new PostCSS 8+ API, this will likely not be an issue. But until then, you may need to downgrade some PostCSS plugins to avoid errors.