If I understand your question you don’t mean validations, but you want to correct your data. In that case you can use the string functions in a “Change Object” activity, like as follows.
All to upper case and trim whitespace at the beginning and at the end of the string:
All to upper case and remove all spaces from string:
toUpperCase(replaceAll($Object/Attribute, ' ', ''))
All to upper case and remove all spaces, tabs, line breaks from string:
toUpperCase(replaceAll($Object/Attribute, '[\s]', ''))
Use can use toUppercase functionality inside you microflow activity
Step1 : Create a string variable, which get the User input by the object it is passed from the page
Step2: From the Created variable use toUppercase($input/string)
The above link might help you in detail
I would highly recommend following the “become a rapid developer” learning path, and specifically this part:
Validation in microflows is a basic functionality that you will be using in virtually every application that allows user input (and in some that don't), so it's definitely worth learning how to do it properly.
As for other validation you might want to do, depending on your usecase: