Kindly help me in this regard.
I wouldn't link the choice of software architecture (e.g. Micro-Services vs. Monolith) with the choice of software development lifecycle or project management (e.g. Agile vs. Waterfall).
A software architecture should be chosen based on the quality attributes of the product, taking into account the tradeoffs between performance, security, ease-of-use, availability, interoperability, maintainability, etc...
Software development procedures, management styles, and organization units should be chosen and built based on what makes the team most productive. A great Scrum team may prefer to do micro-services in one project, and a monolith in another project. Likewise, a company that follows a waterfall process may choose to break an application to microservices or leave it as a monolith.
The difference between Agile and Waterfall might be the way in which the architecture emerges: In Waterfall, people often do more architecture upfront, whereas in Agile, there is some architecture upfront, but more of the architecture emerges as requirements are discovered during the sprints.