Longtable with numbered list without using preset counter names

I am trying to make a longtable to list out publications but I want to use arabic numerals combined with latin capital letters for different categories. This is what I have for only a few items, but I would like to keep updating this so that the newer entries are first and it will be tedious to keep adding them by hand when the numbers get larger.

documentclass{article}
usepackage{longtable}
usepackage{xcolor}
%http://www.procato.com/rgbfind/
definecolor{navy_blue}{rgb}{0, 0, 0.502}

begin{document}

noindent begin{longtable}{@{} p{.3in} l}
multicolumn{2}{l}{textcolor{navy_blue}{Large{textbf{Publications}}}} 
multicolumn{2}{l}{Large{underline{Journal Articles}}} 

(J1) & parbox{6.2in}{large{textbf{Author 1}, Author 2 (year). Title. textit{Journal} 
(J2) & parbox{6.2in}{large{textbf{Author 1}, Author 2, Author 3 (year). Title. textit{Journal} 

multicolumn{2}{l}{Large{underline{Conference Abstracts with Presentations}}} 

(A1) & parbox{6.2in}{large{textbf{Author 1}, Author 2 (year). Title. textit{Conference} 

end{longtable}

end{document}

I think I can include an enumerate in place of (J1), (J2), etc., but I’m not clear how to make these specific numbering styles. I’ve tried following the documentation on Overleaf to at least get some basic numbering to work but I’m getting an error. This MWE below is just my effort to get some numbers going, and is not an effort to get the numbering style working yet.

noindent begin{longtable}{@{} p{.3in} l}
multicolumn{2}{l}{textcolor{navy_blue}{Large{textbf{Publications}}}} 
multicolumn{2}{l}{Large{underline{Journal Articles}}} 

begin{enumerate}

item & parbox{6.2in}{large{textbf{Author 1}, Author 2 (year). Title. textit{Journal} 
    
end{enumerate}

end{longtable}

The error says that item is missing but it’s not and that there might be some extra } in my code.