In my country there are very few manufacturing factories,but large numbers of small retail shops (like one shop per house or may be even more). What are the effects in the economy of a country for having large numbers of retail shops,but very few manufacturing factories ?
Economists are generally more interested in the aggregate output of different sectors of the economy rather than the number of firms or outlets. The difference between lots of small shops and a few large shops is quite different to the difference between the majority of GDP coming from industry or services.
If a country has a lot of small retail outlets and a few large manufacturing firms, that suggests that there are much larger economies of scale in manufacturing than retail.
The aggregate output of agriculture, industry and services are normally reported in GDP tables (here's an example for Rwanda).
A larger services sector is normally associated with richer, more advanced countries. These images compare countries based on the relative size of industry, services and agriculture, and the proportion of the labour force working in each:
In poorer countries, agriculture tends to be lower productivity than other sectors, so those countries tend to show up as greener in the labour share than the GDP chart.