Please use =upper(enter the cell address which you have the small letter) then drag to the next cell in horizontal and verical. text will show you in upper case.
MS Excel has certain built-in functions to perform this change :- UPPER - Converts all lowercase letters in a text string to uppercase.
PROPER - Capitalizes the first letter in a text string and any other letters in text that follow any character other than a letter. Converts all other letters to lowercase letters.