Rephrase instructions for exercise `convertbase`

subjects/convertbase/README.md

@@ -2,7 +2,10 @@
 
 ### Instructions
 
-Write a function that returns the conversion of a `string` number from one `string` baseFrom to one `string` baseTo.
+Write a function that receives three arguments:
+- `nbr`: A string representing a numberic value in a [base](https://simple.wikipedia.org/wiki/Base_(mathematics)).
+- `baseFrom`: A string representing the base `nbr` it's using.
+- `baseTo`: A string representing the base `nbr` should be represented in the returned value.
 
 Only valid bases will be tested.