Here is a first draft. I had to replace Candara by another font, as there's no package to use it with pdflatex (however, it can be used with fontspec and xe/lualatex):
\documentclass[twoside, 11pt]{book}\usepackage[utf8]{inputenc}\usepackage[T1]{fontenc}\usepackage[vmargin= 1.25cm, left = 3.5cm, right = 1.25cm, showframe]{geometry}\usepackage{titlecaps}\setcounter{secnumdepth} {3}\pagestyle{plain}\usepackage{amsmath, amsthm, bookmark}%\usepackage{newpxtext, newpxmath}\usepackage{graphicx}\graphicspath{{figures/}}%\usepackage[explicit]{titlesec} \usepackage{titletoc}\titleformat{\chapter}[block]{\fontfamily{verdana}\fontsize{27pt}{34pt}\selectfont\filleft}{\thechapter.}{0.5em}{#1}\titleformat{name=\chapter, numberless}[block]{\fontfamily{verdana}\fontsize{27pt}{34pt}\selectfont\filleft}{}{0em}{#1}\titlespacing{\chapter}{0pt}{12pt plus 2pt minus 2pt}{36pt}\titleformat{\section}{\fontfamily{verdana}\Large}{\thesection}{0.5em}{#1}\titleformat{name=\section, numberless}{\fontfamily{verdana}\Large}{}{0em}{\addcontentsline{toc}{section}{#1}#1}\titleformat{\subsection}{\fontfamily{verdana}\large}{\thesubsection}{0.5em}{#1} \titleformat{name=\subsection, numberless}{\fontfamily{verdana}\large}{}{0em}{\addcontentsline{toc}{subsection}{#1}#1} \titleformat{\subsubsection}{\fontfamily{verdana}\large}{\thesubsubsection}{0.5em}{#1}\renewcommand\thesubsubsection{(\alph{subsubsection})}\titlecontents{chapter} [0em] %{\bigskip\fontfamily{verdana}\selectfont \bfseries}{\thecontentslabel\quad}%\thecontentslabel{}% numberless{\hfill\contentspage}[\smallskip] %\titlecontents{section} [1.667em] %{\medskip\fontfamily{verdana}\selectfont}{\thecontentslabel\enspace}%\thecontentslabel{\hspace*{2.12em}}%numberless{\titlerule*[1pc]{.}\contentspage}[\smallskip]%\titlecontents{subsection} [3.76em] %{\medskip\fontfamily{verdana}\selectfont}{\thecontentslabel\enspace}%\thecontentslabel{\hspace*{3.12em}}%numberless{\titlerule*[1pc]{.}\contentspage}[\smallskip]%\begin{document}\tableofcontents\chapter{Review of Literature}\section{Preliminaries of Graph theory} A graph $G = (V(G), E(G))$ is a\section*{An unnumbered section}\subsection{Different Kinds of Graphs}\subsection*{Other Kinds of Graphs}\subsubsection{A test subsub}\end{document} 
