%Sayyed Ahmad Mousavi
\documentclass{article}
\usepackage[leqno]{amsmath}
\usepackage{enumitem}
\newtheorem{thm}{Theorem}[section]
\numberwithin{equation}{section}

\begin{document}
    \section{Section 1}
    
     \begin{equation}
        a + b = c
    \end{equation}
     \begin{equation}
        a + b = c
    \end{equation}
    \begin{equation}
        a + b = c
    \end{equation}

\begin{thm}
This is a sample This is a sample This is a sample This is a sample This is a sample This is a sample This is a sample This is a sample
    \begin{enumerate}[leftmargin=*,rightmargin=2cm,label=\normalfont{(\theequation)},labelsep=1cm]
    \refstepcounter{equation}
        \item  This is  $c + d = e$ This is This is  $c + d = e$ This is  This is  $c + d = e$ This is  This is  $c + d = e$ This is  This is  $c + d = e$ This is  This is  $c + d = e$ This is This is  $c + d = e$ This is This is  $c + d = e$ This is 
    \end{enumerate}
This is a sample This is a sample This is a sample This is a sample This is a sample This is a sample This is a sample This is a sample
\end{thm}

    \begin{equation}
        1 + 1 = 2
    \end{equation}
\end{document}