Hi Denise,
/course/format/grid/Readme.md - quick link: https://github.com/gjb2048/moodle-format_grid/blob/master/Readme.md#installation
Which relates to what the reported error screen is telling you. All of which are out of my control. They look to me like straightforward Unix / Apache administration / configuration solutions that match the instruction in the readme file.
Gareth