To write any research paper, you must first read several published papers. Each type of scholarly article is written in a specific style, and you need to understand and be able to write in that style. Since you are planning to write an experimental report or a lab report, you should read several such published reports. Once you are familiar with this kind of article, you will have a clear idea of how to write your paper.
Generally, an experimental paper or an experimental report is structured as follows:
Introduction: The introduction states the problem and purpose of the study and frames the research question.
Related Work: Give a brief overview of related work in the field. This will be similar to a literature search, but slightly less exhaustive.
Experimental Design: Explain the study design and why you think the design was suitable for the problem.
Methods & materials: Give a detailed explanation of how the experiment was conducted and the materials used. Make sure you include every small detail so that someone else can replicate the experiment if required.
Results and Discussion: This section includes the results of the experiment, and disusses its implications.
Here are some resources that you might find useful: