Man pages matching name pcre2_substring_copy_bynumber in section 3:

pcre2_substring_copy_bynumber.3.en	debian 10 / libpcre2-dev
pcre2_substring_copy_bynumber.3.en	debian 11 / libpcre2-dev
pcre2_substring_copy_bynumber.3.en	debian 12 / libpcre2-dev