Not Declared in this Scope with Multiple .ino Files

I recently came across a post regarding the use of multiple .ino files in a project, which made my life so much easier in a sense of code cleanup. However, I'm having a bit of an issue that I haven't been able to find an answer for (Perhaps I'm just searching the incorrect terminology?). As I know with a standard 1-file sketch, a function needs to be defined chronologically-before it's called anywhere.

However, how does that come into play if I have multiple files (I'm going to refer to them as classes from here on out since I;m a Java guy)? I have 3 classes right now, a Main, an SQLInsert, and tools. In my SQLInsert file, I have a call to a function formatString(). This function declaration resides in my Tools file. When I call it, however, I get:

'formatString' was not declared in this scope

How can I ensure that the arduino is made aware of that function before it gets to the call for it, seeing as they are in different classes? Does it require a sort of pointer in the SQLInsert class? Thanks in advance.

For reference, here is the code for the function I am trying to call:

TOOLS.INO
-------------
String formatString(String input, String sub1, String sub2) {
  CODE HAPPENS HERE!
}

SQLINSERT.INO
------------------
String getStmt = formatString(...);

CONSOLE
-----------
'formatString' was not declared in this scope

It's not anything like classes. It's like copy-pasting all the text together in a big lump.

There is an order to the lump: the "primary" INO file with the same name as the folder will be first, followed by the others in alphabetical order. Global variables which must be accessed by more than one .ino should go into that primary one. Often you will set it up so that's all that it contains. (It does not have to contain setup() and loop() but it's usually convenient to put them there.)

MorganS:
It's not anything like classes. It's like copy-pasting all the text together in a big lump.

There is an order to the lump: the "primary" INO file with the same name as the folder will be first, followed by the others in alphabetical order. Global variables which must be accessed by more than one .ino should go into that primary one. Often you will set it up so that's all that it contains. (It does not have to contain setup() and loop() but it's usually convenient to put them there.)

Ah, so there is a method to the madness of how it loads them up. I know they don't function like classes at all, it was more general terminology since I couldn't find a good word for what it does.

Thank you for the information on how it loads it up though. I rearranged and renamed some things and it's working well now.