The scientific notation is not displayed in SQL Server when float is turned to varchar

The solution for converting float to varchar into a scientific counting method in MSSQL

When the system was initialized, because of a colleague, there was no single quotation mark in front of the numeric data, resulting in a float type after entering the database
We need to make the following conversions to change the data to a varchar type

DECLARE @a float//define a float variable
Set @a = 13824658956//Assign value float variable
Select @a as a//display variable
Select CONVERT (varchar, @a) as a//display by string
Select CONVERT (Decimal (18,0), @a) as a//display by decimal digit count
Select CONVERT (Varchar,convert (decimal (18,0), @a)) as A//convert string display
　

The scientific notation is not displayed in SQL Server when float is turned to varchar