How to add numbering in squared brackets to bibliography list?

Question

I am writing a manuscript to be published in a scientific journal. For this, I am using the Springer Latex Template. The cited references appear ordered by appearance in the final bibliography list. However, the numbering in squared brackets prior to each entry is missing. So, this is how it looks at the moment:

Here is a small example:

\documentclass{article}

\usepackage[natbibapa]{apacite}

\bibliographystyle{sn-apacite}


\begin{document}

Hello world [\citenum{Ljunggren2002}]
Hello world [\citenum{Anthony2000}]



\begin{thebibliography}{}
    \providecommand{\doi}[1]{\url{https://doi.org/#1}}
    
    \bibitem [\protect \citeauthoryear {%
        Ljunggren%
        \ \BBA {} {\AA}gren%
    }{%
        Ljunggren%
        \ \BBA {} {\AA}gren%
    }{%
        {\protect \APACyear {2002}}%
    }]{%
        Ljunggren2002}
    \APACinsertmetastar {%
        Ljunggren2002}%
    \begin{APACrefauthors}%
        Ljunggren, F.%
        \BCBT {}\ \BBA {} {\AA}gren, A.%
    \end{APACrefauthors}%
    \unskip\
    \newblock
    \APACrefYearMonthDay{2002}{}{}.
    \newblock
    {\BBOQ}\APACrefatitle {Development of a new damper to reduce resonant
        vibrations in lightweight steel joist floors} {Development of a new damper to
        reduce resonant vibrations in lightweight steel joist floors}.{\BBCQ}
    \newblock
    \APACjournalVolNumPages{Applied Acoustics}{63}{11}{1267-1280}.
    \newblock
    
    \newblock
    
    \PrintBackRefs{\CurrentBib}
    
    \bibitem [\protect \citeauthoryear {%
        Anthony%
        , Elliott%
        \BCBL {}\ \BBA {} Keane%
    }{%
        Anthony%
        \ \protect \BOthers {.}}{%
        {\protect \APACyear {2000}}%
    }]{%
        Anthony2000}
    \APACinsertmetastar {%
        Anthony2000}%
    \begin{APACrefauthors}%
        Anthony, D.%
        , Elliott, S.%
        \BCBL {} Keane, A.%
    \end{APACrefauthors}%
    \unskip\
    \newblock
    \APACrefYearMonthDay{2000}{}{}.
    \newblock
    {\BBOQ}\APACrefatitle {Robustness of optimal design solutions to reduce
        vibration transmission in a lightweight 2-D structure, part i: Geometric
        design} {Robustness of optimal design solutions to reduce vibration
        transmission in a lightweight 2-d structure, part i: Geometric
        design}.{\BBCQ}
    \newblock
    \APACjournalVolNumPages{Journal of Sound and Vibration}{229}{3}{505-528}.
    \newblock
    
    \newblock
    
    \PrintBackRefs{\CurrentBib}

\end{thebibliography}
    
\end{document}

How can I add the missing numbering in squared brackets?

The apacite.bst file that I used is part of the Springer Latex Template and can be downloaded here: https://www.springernature.com/gp/authors/campaigns/latex-author-support

Thanks in advance!