Update
Now there is a MWE in the question and I know that TOC entries for TOC, LOF and LOT etc. are required. But I do not understand what the comment
The alignment between the numbering and title needs to be in line as well
means. So it is still a guess what the desired result is.
\documentclass[11pt,a4paper,oneside]{book}
\usepackage{blindtext}% only for dummy text
\pagestyle{plain}
\usepackage[utf8]{inputenc}
\usepackage[margin=20mm,left=30mm]{geometry}
\usepackage{parskip}
\usepackage[onehalfspacing]{setspace}
\usepackage{tocbibind}
\usepackage{tocbasic}
\usepackage{expl3}
\usepackage{hyperref}% <- should be the last package
\ExplSyntaxOn
\clist_map_inline:nn
{chapter,section,subsection,subsubsection,paragraph,subparagraph}
{\DeclareTOCStyleEntry[indent=0pt,numwidth=3.8em]{tocline}{#1}}
\clist_map_inline:nn
{figure,table}
{\DeclareTOCStyleEntry[indent=0pt]{tocline}{#1}}
\ExplSyntaxOff
\DeclareTOCStyleEntry[%
level=\chaptertocdepth,%
beforeskip=0pt plus .2pt,%
indent=0em,%
numwidth=3.8em,%
entryformat=\textbf,%
pagenumberformat=\textbf,%
linefill=\hfill
]{tocline}{fmchapter}
\makeatletter
\let\l@origchapter\l@chapter
\newcommand*\usefmchapter{% define switch to fmchapter entry
\addtocontents{toc}{%
\protect\addvspace{1em plus 1pt}% additional space in TOC before the first fmchapter entry
\protect\let\protect\l@chapter\protect\l@fmchapter
}%
}
\newcommand*\useorigchapter{% define switch to original chapter entry
\addtocontents{toc}{%
\protect\let\protect\l@chapter\protect\l@origchapter
}%
}
\makeatother
\begin{document}
\usefmchapter% <- switch
\tableofcontents
\listoffigures
\listoftables
\addcontentsline{toc}{chapter}{Dedication}
\blindtext
\addcontentsline{toc}{chapter}{BLahBlah}
\blindtext
\addcontentsline{toc}{chapter}{BLahBlahBlah}
\blindtext
\useorigchapter% <- switch
\blinddocument
\usefmchapter% <- switch
\addcontentsline{toc}{chapter}{Conclusion}
\blindtext
\addcontentsline{toc}{chapter}{BLahBlah}
\blindtext
\addcontentsline{toc}{chapter}{BLahBlahBlah}
\blindtext
\end{document}
Result:

Note that you can/have to adjust numwidth=3.8em
to your needs.
But if you want

then you have to use the value of numwidth
for indent
of fmchapter
:
\DeclareTOCStyleEntry[%
level=\chaptertocdepth,%
beforeskip=0pt plus .2pt,%
indent=3.8em,% <- changed
numwidth=3.8em,%
entryformat=\textbf,%
pagenumberformat=\textbf,%
linefill=\hfill
]{tocline}{fmchapter}
Original answer
Unfortunaly there is no MWE in the question, so it is only a guess.
The following suggestion uses package tocbasic
to declare an additional entry style in TOC:
\documentclass[11pt,oneside]{book}
\pagestyle{plain}
\usepackage{tocbasic}
\usepackage{expl3}
\ExplSyntaxOn
\clist_map_inline:nn
{chapter,section,subsection,subsubsection,paragraph,subparagraph}
{\DeclareTOCStyleEntry[indent=0pt]{tocline}{#1}}
\ExplSyntaxOff
\DeclareTOCStyleEntry[%
level=\chaptertocdepth,%
beforeskip=0pt plus .2pt,%
indent=0pt,%
numwidth=1.5em,%
entryformat=\textbf,%
pagenumberformat=\textbf,%
linefill=\hfill
]{tocline}{fmchapter}
\usepackage{blindtext}% only for dummy text
\begin{document}
\tableofcontents
\chapter*{Declaration}\addcontentsline{toc}{fmchapter}{Declaration}
\blindtext
\chapter*{Abstract}\addcontentsline{toc}{fmchapter}{Abstract}
\blindtext
\chapter*{Dedication}\addcontentsline{toc}{fmchapter}{Dedication}
\blindtext
\blinddocument
\end{document}
Result:
