That is not the case, metafor is not part of the base R installation, it is a separate package that you need to install along with it's dependencies (i.e. matrix). Anyhow, in the screenshot you are posting (which is a bad practice here, post formatted code instead) there is no error message or request to install matrix since it seems is already installed.
Since you are not clearly stating what your actual problem is, we are not able to help you, please try to provide a REPRoducible EXample (reprex) illustrating your issue.