Error copy and WCAG compliance

morning all!

looking for a suggestion on some issues if it still fails WCAG compliance.

Recently, one of the forms with all mandatory fields has been designed, and
everything is correct. For example, having an asterisk to all required
fields and also providing clear information at the top.
However when the form is submitted with empty entries, below all fields
show an error message as "this field mandatory", per my understanding,  we
should use something like "first name is required"- mentioning that
specific input should be clearly specified in error copy- is there
guideline where this has been mentioned, which I can use to prove my point.

I believe 3..3.1 and 3.3. 4 ? correct?

please correct and guide me if I am missing something.

Thanks.